FLOW PATTERN ENHANCER SYSTEM FOR GAS WELLS WITH LIQUID LOAD PROBLEMS

Abstract

A flow pattern enhancer system mainly for gas-producing oil wells with liquid load problems, comprising mechanical elements that atomize the liquids accumulated at the bottom of the well facilitating their transport to the surface, by decreasing frictional pressure drops and weight of the hydrostatic column.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119 of Mexican Patent Application No. MX/a/2011/008907, filed Aug. 24, 2011, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a flow pattern enhancer system mainly useful in gas-producing oil wells with liquid load problems, comprising mechanical elements for atomizing the liquids accumulated at the bottom of the well, and facilitating its transport to surface, caused by the decrease of the frictional pressure drop and weight of the hydrostatic column.

BACKGROUND OF THE INVENTION

The accumulation of liquids in the gas wells occurs naturally because the decrease of deposit energy during their productive lives, caused by the decrease of the deposit pressure and thus the expenditure produced by the well. While the production expenditure is maintained above the critical expenditure, the liquids will be carried to the surface and won't be accumulated at the bottom of the well.

The liquid load in a gas well is also related to the change of flow type, the big pressure drops through the production pipes are caused by fluctuations in the gas and liquid transport, being normally called these fluctuations potholes. The distribution of the liquid and gas phases simultaneously flowing through a piping, may be classified by its form and rate and are called flow patterns.

The parameters affecting in the formation of the liquid load in a gas well are the following:

Static pressure of the deposit.

Pressure at the wellhead.

Pressure at the discharge line.

Diameter of the production pipe.

In Mexico, in order to solve the gas deposit exploitation issues with liquid load problems, at present liquid recovery systems are applied, allowing the extraction of the liquids of the bottom of the wells. Its correct selection will depend mainly of the well characteristics, although all are aimed to solve the same problem, they don't work under the same conditions; generally, the artificial systems of production have a technical and temporary range therefore always be sought the one working longer, optimally and at lower cost, without being this an impediment to use different systems during the productive life of the well.

The state of the art in solving the gas deposits exploitation issues with liquid load problems, mainly reports the following technologies:

Small Tubing

Small tubing is a piping of smaller diameter than the production piping, this is introduced in the well in order to reduce the flow area for maintaining the expenditure above the critical value. Good yields have been observed in wells with low production volume, in which the frictional losses are not very significant.

The leading disadvantage of this system, besides an unstable production, is that it stops working optimally in a short time, so if it is not combined with other system, it is only a temporary solution.

Foaming Agents/Reactive Liquids

Both methods consist on the introduction of surfactants or foaming agents in the well to reduce the surface tension of the fluids and form foams. When this happens, the liquid column becomes foam, becoming lighter and facilitating its transport to the surface; however, in spite of obtaining good result for water, in case of the condensates it has been difficult to obtain a substance to make them foamy, so this is the reason why it is not convenient to apply this system in wells with water cut below 80%.

This system is mainly used in wells with a very low expenditure of production due to the hanging and the high pressure drops along the piping, however it is not advisable to use in wells with problems of emulsified liquids because the investment in the surfactant products may be small compared to the necessary for the products breaking the emulsions formed. The introduction of foaming bars is performed through the Production tubing (TP) and the reagents are injected by a capillary tubing, the can be injected in the zone of triggers or at the end of the TP.

Plunger Lift

Used mainly in wells with intermittent production, the plunger lift generates a mechanical interface between gas and liquid. At the beginning, the well is closed and the plunger is on the surface dropping it inside the TP, in its way down, the plunger allows the pass of liquid above it preventing its return; once at the bottom the pressure generated by the gas under the plunger is increased until it matches the pressure of the motor valve opening of the well located on the surface. Once the well is opened, the plunger travels along the production tubing displacing the liquid pothole; afterwards the well is closed (by indication of the motor valve) and the plunger falls to the bottom to start again the cycle. During its travel, this plunger is touching internally the tubing freeing it of paraffins, salts, carbonates, etc., that may deposit in the interior of the same.

It is important for this system that the well produces its fluids with a relation gas-oil (RGA) and pressure enough to lift the potholes of liquid; for the case of pipe sizes, this system can work with big sizes, being this a disadvantage in the other systems.

Compressors Installed at the Mouth of the Well (Compressors)

The compression increases the gas velocity to be equal or greater than the critical velocity and at the same time decreases the pressure flowing in the wellhead causing the pressure in the side of the deposit near the well to decrease as well and extends the life of the well.

There are many types of compressors varying according to the initial investment, operating costs and functionality of each particular well.

Hydraulic Pumping

In this system, energy is transmitted from a motor fluid to the fluids contained in the well for its extraction; a pump on the surface transmits dynamic energy to the motor fluid introduced in the well, wherein it mixes with the fluids therein and by a pump at the bottom, this mixture is impelled to the surface where it enters to a separator sending the well fluids out of the system and the motor fluid again to the pump on the surface.

This system does not present a depth limit for its application and it is applicable in deviated wells.

For gas wells, the pump located at the bottom must be Jet type because the reciprocating pump doesn't admit gas and has to open a line to vent it. The jet type pumps reduce the pressure in the side of the Formation increasing the velocity of the fluid introduced in them.

Gas Lift

In this system, gas is injected to the well to a certain depth. The gas is mixed with the liquid column making it lighter, due to this, its pressure at the bottom is reduce, causing the pressure from the deposit to be enough to push the column to the surface.

Although it is not achieved to reduce the pressure at the bottom of the well as with other pumping systems, the gas lift is outstanding because of its versatility and due to this is a good candidate in certain conditions. While other pumping systems become inefficient for high values of the gas-liquid relation (RGL), in this case a big amount of gas from the deposit will directly decrease the volume of gas to be injected; it has no trouble handling solids and can be used in deviated wells although as these become more horizontal, the gas injection doesn't reduce the weight of the liquid column and may increase the frictional pressure losses.

Progressive Cavity Pumps

This system consists mainly of a stator with internal helical form, double entrance and a helical rotor rotating in the stator. The cross section of the rotor is circular and at every point eccentric to the axis; the centers of the sections are supported along a helix, which axis is the rotor axis. Both are linked such that the section of the rotor has a reciprocating movement through the duct of the stator. This movement causes cavities that be formed, which are delimited by a line adjustment between the two elements. When the rotor makes a turn, said cavities arranged in a helical form move, including the liquid to be carried, being independent said cavity from the next one to be form by the adjustment line, therefore avoiding the return of the liquid.

Although this system was designed originally to carry solids and viscous fluids, it has also been used for liquid extraction in gas wells; its applicability is reduced mainly to the following general conditions:

Depths of no more than about 1,250 meters

Relatively high liquid expenditures

Low pumping profile

Low temperatures in the well.

Automated System of Liquid Recovery for Wells Producing Gas and Condensate

It is based on the installation of a small tubing or flexible piping and of a valve control system automated on the surface. The target of this system is to “sweep” the accumulated liquid through a flexible piping (or small tubing) and to produce gas through the production piping; the control valves, registering a pressure differential, act opening and closing the system, so the fluids can be produced continuously and thus avoid the intermittent production of the wells or its definitive closure.

SUMMARY OF THE INVENTION

The present invention is an improvement over the above mentioned technologies, since it relates integrally to the operation principle of a flow pattern enhancer system for use mainly in gas-producing oil wells with problems of liquid load and takes advantage of the deposit energy and its fluids in order to induce a change in the characteristics of the flow pattern of the liquid and gas phases from the bottom of the well, enhancing the transport of liquid through the production piping to reduce the pressure drops in the latter.

Therefore, an object of the present invention is to provide an enhancer system for the flow pattern of gas wells with liquid load problems, comprising mechanical elements atomizing the liquids accumulated at the bottom of the well, facilitating its transport to the surface by decrease of frictional pressure drops and weight of the hydrostatic column.

A further object of the present invention is to provide a flow pattern enhancer system which is used mainly in gas-producing oil wells with liquid load problems.

Yet another object of the present invention is to provide a flow pattern enhancer system located on the lower extremity of the production piping of the gas producing wells with liquid load problems, to displace to the surface the liquids accumulated at the bottom of the well.

The flow pattern enhancer system of the present invention is mainly used in gas wells with liquid load problems, and comprises the following elements:

a) primary expander,

b) homogenization chamber,

c) secondary expander,

d) suction veins, and

e) anchorage and tightness system,

for displacing the liquids accumulated at the bottom of the well to the surface, taking advantage of the same energy of the gas produced, extending the flowing life of the wells in a continuous form and increasing its recovery factor.

The primary expander has a smaller inner diameter than the homogenization chamber, and is connected to the lower part of the homogenization chamber. The homogenization chamber is positioned between the primary expander and the secondary expander, with the primary expander below and the secondary expander above, i.e., its lower part is connected to the primary expander and its upper portion is connected to the secondary expander.

The secondary expander is located above and attached to the homogenation chamber. The secondary expander houses the suction veins, and the upper portion of the secondary expander has a fishing neck. The suction veins are housed in low pressure zones inside the secondary expander and communicate the low pressure zones inside the secondary expander with the liquid accumulated outside the system. The anchorage and tightness systems are coupled in the inside to the primary expander and homogenization chamber and on the upper extreme to the secondary expander.

The anchorage and tightness system enables installation of the flow pattern enhancer system at any depth of the production piping of the well. The anchorage and tightness system forces the flow to take place only inside the flow pattern enhancer system. The flow pattern enhancer system has mechanical anchors which are attached to the piping and elastomeric seals which allow the system to anchor and seal the inside in order to confine the flow completely inside the system.

The flow pattern enhancer system is installed in the lower extremity of the production piping. Thus, the flow pattern enhancer system can be placed below the depth to which bubbling pressure is present. Employment of the flow pattern enhancer system enables increase of the gas velocity to 4-6 m/s, achieving fog flow and a continuous flow structure with liquid droplets dispersed in the continuous gas phase.

When designing the present flow pattern enhancer system, each element depends on three different processes, namely expansion, compression and mixing, and are performed by specific methods consisting primarily on determining the flow areas and geometries thereof. The drag coefficient is determined by the formula:

Drag coefficient=Driving flow/Dragged Flow.

The flow pattern enhancer system of the present invention increases gas production over 300% from the initial production and prevents formation of hydrates, thereby avoiding re-pressure of surface lines because of methane hydrate accumulation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows exterior and interior views of the enhancer system of the flow pattern of gas wells with problems of liquid load of the present invention.

FIG. 2 shows deformation of a liquid drop depending on the value of Weber's number.

FIG. 3 shows the transition of flow type experienced by the gas in the well as the gas velocity decreases.

FIG. 4 shows a diagram of the secondary expander of the present invention.

FIG. 5 shows the behavior of the pressure gradient and productions of the well Cuitlahuac-802 of Activo Integral Burgos, with and without the use of the enhancer system of the flow pattern of gas wells with liquid load problems of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a flow pattern enhancer system useful mainly in gas-producing oil wells with liquid load problems, comprising mechanical elements atomizing the liquids accumulated at the bottom of the well, thereby facilitating their transport to the surface, by decrease of the frictional pressure drops and weight of the hydrostatic column.

FIG. 1 shows exterior and interior views of the enhancer system of the flow pattern applied mainly in gas-producing oil wells with liquid load problems of the present invention, which comprises five mechanical elements (subsystems):

1) Primary expander. It is the first mechanical element, it allows the expansion of the gas stream from the well that is the driving fluid to a state of high speed; that is, it has the function of causing the first pressure drop through a controlled flow restriction, generating the gas expansion from the well, driving the fluid to a state of high speed, caused by the pressure energy of the deposit. The sudden expansion of gas increases the velocity that, in presence of liquid, promotes the formation of a homogenous mix.

2) Homogenization chamber. It is the second mechanical element and it is connected to the primary expander, inside the stabilization and homogenization of the liquid and gas flow from the first stage of expansion are performed, and the fluids are transported through the chamber to the third mechanical element called Secondary expander; that is, it has a larger interior diameter than the Primary expander and it is connected to the Primary expander in the lower part and to the Secondary expander in the upper part, inside the stabilization and homogenization of the liquid and gas flow from the first stage of expansion are performed, the fluids are transported through the chamber to the Secondary expander.

3) Secondary expander. It is the third mechanical element and it is attached to the homogenization chamber, having the function of provoking a second restriction to flow, it has such a geometry that it is increases the gas velocity, forming zones of low pressure inside, where it houses the Suction veins; in the upper part it has a fishing neck, which is the geometry allowing the installation and removal of the enhancer system of the flow pattern inside the production piping.

4) Suction veins. They are the fourth mechanical element; they are located in the low pressure zones of the interior of the Secondary expander and communicate the low pressure zones of the interior of the Secondary expander with the liquid accumulated outside the system; they have the function of allowing the liquid accumulated outside the system to be suctioned by the gas stream (driving fluid) decreasing the particle size of the liquid (atomization process) using the high velocity of the gas stream achieved in the Secondary expander in the low pressure zones.

5) Anchorage and tightness system. It is the fifth mechanical element; it is attached to the primary expander and homogenization chamber on its lower part, and to the secondary expander on its upper part; and it allows to install the enhancer system of the flow pattern at any depth of the production piping of the well and at the same time, it forces the flow to take place only on the inside of all the above-mentioned elements; it has mechanical anchors which are attached to the piping and elastomeric seals allowing the system to anchor and cause tightness outside so that the flow performs completely as mentioned above.

According to the foregoing, the enhancer system of the flow pattern of gas wells with liquid load problems of the present invention, is installed in the lower extreme of the production piping and has the function of causing an increase in the fluid velocity by passing by two restrictions inside the system. It causes expansion of gas flowing along the condensates and/or water. The process allows obtaining a uniform mixture of gas/condensates/water (liquid atomization in the gas), which prevents slippage of gas and pitch problems. Besides it maintains a minimum counter-pressure over the side of formation and reduces the frictional pressure drops.

The enhancer system of flow pattern of the present invention can be placed below the depth to which it has the bubbling pressure and it is useful when you are managing high ratios of dissolved/gas/oil, as in this case the additional amount of released gas helps to “drag” the liquids accumulated at the bottom of the well to the surface, without the requirement of an external energy source.

The flow pattern enhancer system of the present invention uses the latent energy in the dissolved gas, by releasing and expanding to lift the fluids accumulated in the well; when the gas velocity is lower than the minimum drag velocity, there will be liquid runoff at the bottom of the well through the walls of the production piping. When this occurs, the liquids are reincorporated to the gas stream at high velocity when they are introduced to the body of the secondary expander via suction veins, that is, low pressure zones which in turn fractionated, distribute and atomize the liquids in the gas stream.

The enhancer system of the flow pattern of the present invention is based on the principle of conservation of momentum of the streams of involved fluids (gas, condensed hydrocarbons and/or water). The flow pattern enhancer system of the present invention is based on the transmission of impact energy of a fluid at high velocity (gas), against another fluid in motion or at rest (condensates and/or water), to provide a fluid mixture at a moderately high velocity, that decreases until a final pressure greater than the initial of the lower velocity fluid is obtained.

The whole flow pattern enhancer system of the present invention promotes the gas expansion at the bottom of the well, increasing the velocity to what is needed in order to incorporate the existing liquids in atomized form through the production piping to the surface. Such velocity is termed “critical velocity”. On this regimen the liquid drops move inside the gas stream being subjected to the gravity and drag forces, fragmenting the liquid particles by the effects of incorporation through the suction veins and secondary expander, while the superficial tension of the liquid acts to avoid its fragmentation (surface pressure). The antagonism of the two pressures determines the maximum measure that a drop can achieve, being represented as:

• • Velocity pressure: ν_G² ρ_G
  • Surface pressure: σ/d
    where:
• ν_G: velocity at which the drop of liquid is displaced in the gas
• ρ: density of the gas
• σ: surface tension of the drop of liquid
• d: diameter of the drop of liquid

These two pressures make up the Weber's (We), which is a dimensionless number useful on the analysis of flows wherein there is a surface between two different fluids.

$\begin{array}{cc}\mathrm{We}=\frac{v_G^2{\rho }_Gd}{\sigma g_c}& \left(1\right)\end{array}$

If this number exceeds the critical value, the drop of liquid will be fragmented, the critical value for the free fall of a drop is between 20 and 30.

With a Weber's number within the critical range, the deformation of drops of the liquid at high velocities of the gas stream is considered a spherical shape; if the Weber's number is under 20 or above 30, there will be a pressure difference at the sides of the liquid drop causing it to deform, which is clearly seen in FIG. 2.

The total gravity force is represented by the following equation:

$\begin{array}{cc}{F}_g=\frac{g}{g_c}\left({\rho }_L-{\rho }_G\right)\times \frac{\pi d^3}{6}& \left(2\right)\end{array}$

and the total drag force is given by:

$\begin{array}{cc}{F}_d=\frac{1}{2g_c}{\rho }_GC_a{A\left(v_G-v_L\right)}^2& \left(3\right)\end{array}$

where:

• g: gravitational constant
• d: diameter of the drop of liquid
• ρ_L: density of liquid
• ρ_G: density of gas
• C_a: drag coefficient
• A: cross-sectional area of the drop of liquid
• ν_G: velocity of gas
• ν_L: velocity of drop of liquid

The critical velocity of gas for transporting the drop of liquid of the well bottom is defined as the velocity at which the drop will be suspended in the gas stream. Therefore, the critical velocity of gas ν_G is the velocity at which ν_L=0, if the velocity of the drop of liquid is zero, the net force on it is zero. The equation defining this concept of critical velocity is the following:

F_g=F_d   (4)

Substituting both forces values:

$\begin{array}{cc}\frac{g}{g_c}\left({\rho }_L-{\rho }_G\right)\times \frac{\pi d^3}{6}=\frac{1}{2g_c}{\rho }_GC_a{\mathrm{Av}}_C^2& \left(5\right)\end{array}$

Rewriting the area A=πd²/4 and solving for ν_C:

$\begin{array}{cc}{v}_C=\sqrt{\frac{4g\left({\rho }_L-{\rho }_G\right)d}{\beta p_GC_H}}& \left(6\right)\end{array}$

This equation considers known a liquid drop diameter. Actually, the liquid drop diameter depends on the gas velocity, but the Weber's number can be obtained.

When Weber's number is 30, substituting ν_G for ν_C and clearing d:

$\begin{array}{cc}d=30\frac{\sigma g_c}{{\rho }_gv_C^2}& \left(7\right)\end{array}$

Substituting this equation on Equation 6:

$\begin{array}{cc}{v}_C=\sqrt{\frac{4}{3}\frac{\left({\rho }_L-{\rho }_G\right)}{{\rho }_G}}\frac{\beta }{C_a}30\frac{\rho g_c}{{\rho }_Gv_C^2}\mathrm{or}& \left(8\right)\\ v_C={\left(\frac{40gg_c}{C_a}\right)}^{1\text{/}4}{\left(\frac{{\rho }_L-{\rho }_G}{{\rho }_G^2}\sigma \right)}^{1\text{/}4}& \left(9\right)\end{array}$

Considering a drag coefficient C_a of 0.44, which corresponds to the value used for a completely turbulent flow. Substituting the drag coefficient for turbulent flow and the g and gc values we have:

$\begin{array}{cc}{v}_C=17.514{\left(\frac{{\rho }_L-{\rho }_G}{{\rho }_G^2}\sigma \right)}^{1\text{/}4}& \left(10\right)\end{array}$

where:

• ρ_L: liquid density (lb_m/ft³)
• ρ_G: gas density (lb_m/ft³)
• σ: surface tension (lb_f/ft)
• ν_C: critical velocity of gas (ft/s)

If using the surface tension in dyne/cm units is desired, by using the conversion (lb_f/ft)=0.00006852(dyne/cm) it is obtained:

$\begin{array}{cc}{v}_C=1.593{\left(\frac{{\rho }_L-{\rho }_G}{{\rho }_g^2}\sigma \right)}^{1\text{/}4}& \left(11\right)\end{array}$

where all the variables keep the units of Equation 10 but σ.

Once the critical gas velocity is known, the critical expenditure can be calculated that is a more practical value for its applicability:

$\begin{array}{cc}{q}_C=\frac{3.067{\mathrm{pv}}_CA}{\left(T+460\right)g}& \left(12\right)\end{array}$

where:

• A: cross-sectional area of the inside of the production piping (ft²)
• P: pressure on the wellhead (lb/pg²)
• T: temperature in the wellhead (° F.)
• q_C: critical expenditure of gas (mmft³/day)

The predictions of critical velocity of wells with low pressures in the wellhead are more uncertain.

There are two versions of correlations, one for water and one for condensed hydrocarbons:

$\begin{array}{cc}{v}_{g,\mathrm{water}}=\frac{5.62{\left(67-0.0031p\right)}^{1\text{/}4}}{{\left(0.0031p\right)}^{1\text{/}2}}& \left(13\right)\\ v_{g,\mathrm{condensed}\mathrm{hcns}}=\frac{4.02{\left(45-0.0031p\right)}^{1\text{/}4}}{{\left(0.0031p\right)}^{1\text{/}2}}& \left(14\right)\end{array}$

where:

• p: flowing pressure in the wellhead (lb/pg²)
• ν_g: critical gas velocity (ft/s).

The coefficients 5.321 and 4.043 can be considered respectively for water and hydrocarbons besides the correlation of critical velocity, obtaining the critical gas expenditure as follows:

$\begin{array}{cc}{q}_{C,\mathrm{gas}+\mathrm{water}}=\frac{0.0676{\mathrm{pdt}}_t^2}{\left(T+460\right)z}\frac{{\left(45-0.0031p\right)}^{1\text{/}4}}{{\left(0.0031p\right)}^{1\text{/}2}}& \left(15\right)\\ q_{C,\mathrm{gas}+\mathrm{condensed}\mathrm{hcs}}=\frac{0.0890{\mathrm{pdt}}_t^2}{\left(T+460\right)z}\frac{{\left(67-0.0031p\right)}^{1\text{/}4}}{{\left(0.0031p\right)}^{1\text{/}2}}& \left(16\right)\end{array}$

While the expenditure of fluids in a well is above the critical expenditure, there won't be a formation of liquid column at the bottom of the well.

FIG. 3 shows the transition of a flow type that a gas in the well experiences as the gas velocity decreases.

Based on the above, it can be established that the flow pattern enhancer system of the present invention increases the gas velocity promoting the liquid atomization, with a flow velocity relatively high of 4-6 m/s, achieving fog flow and a continuous flow structure (in the continuous gas phase there are liquid drops dispersed). The gas expenditure is enough to lift the liquid (water and condensate) to the surface. If the liquid drops flow in the same direction of gas, there is a mist flow structure and if the liquid drops have a turbulent flow, it can be called foaming or atomized structure.

The secondary expander showed on FIG. 4, includes the entrance section of the liquid stream; in this chamber it is dragged by the driving fluid (high velocity gas). The mixing chamber allows the intimate mixing between the driving and dragged fluids.

The design calculations consider three different processes: expansion, compression and mixing, so there are specific methods for each type of element, consisting primarily on determining the flow areas and its geometry. Once the equipment is designed, it must operate at steady state conditions for which it was designed and the fundamental calculation is the drag coefficient:

Drag coefficient=Driving flow/Dragged flow

Based on the above, the enhancer system of flow pattern of gas wells with liquid load problems of the present invention solves the problems caused by the liquid accumulation at the bottom of wells, taking advantage of the same energy of the gas produced to “sweep” the accumulated liquid, so the fluids be produced in a continuous form and therefore prevent the intermittent production of wells or its the definitive closure, extending the flowing life thereof and thereby increasing the recovery factor reflected on the incorporation of gas reserves allowing the utilization of more energy resources.

The flow pattern enhancer system of the invention provides primarily the following associated benefits:

a) Increases the recovery factor of well hydrocarbons, due to the reduction in the pressure requirement needed to administer the energy of the deposit;

b) Increases the lifting velocity of the produced fluids to a relatively high flow velocity of gas of 4-6 m/s; the gas expansion flows along with the condensed hydrocarbons and water, generating an uniform atomized mixture with lower density, which reduces the pressure gradient flowing in the production piping;

c) Increases the gas production, as the well production is continuous with a steady behavior even during the liquid discharge, it has a remarkable improvement in the flow pattern in the production piping by generating a homogenous dispersion of both phases;

d) Decreases the pressure drops along the production piping, as it is not allowed that the liquid accumulates at the bottom of the well;

e) Preserves the deposit energy due to the increase of the bottom pressure flowing;

f) Maintains the liquid production with a steady behavior caused by an improvement in the flow pattern of fluids along the production piping; and

g) Extends the flowing life of the wells as it preserves the energy in the deposit by reducing the pressure drops along the production piping.

The following describes a practical example to have a better understanding of the same, without limiting its scope.

EXAMPLE

The application of the enhancer system of flow pattern of gas wells with liquid load problems was made, in the well Cuitlahuac-802 of Activo Integral Burgos. In this well the liquid accumulation is a widespread problem at the Cuitlahuac field due to its conditions of pressure, production and compositions of the produced fluids.

The activities performed for the installation of the enhancer system of patter flow of the present invention consisted on:

1) Well selection: For the selection of the well, those wells having enough information to perform a simulation of the behavior of the flow pattern enhancer are identified, and identify which did not have installed another system obstructing the production piping.

2) Simulation of the production conditions of the well. The simulation was performed based on a finite element, in order to determine the production conditions of the well and determine the optimum installation depth, as well as the diameters of the flow restrictions, both upper and lower.

3) Design and manufacture of the enhancer system of flow pattern. The suitable enhancer system of flow patter for the conditions of pressure, temperature, depth and properties of the fluids produced by the well was designed and manufactured.

Technical Specifications of the Enhancer System of Flow Pattern for the Cuitlahuac-802 Well of Activo Integral Burgos:

a) Operating differential pressure of 7,000 psi.

b) Maximum working pressure of 11,000 psi.

c) Maximum operating temperature of 177° C. (350° F.)

d) Installed and released with steel line.

e) Interchangeable components and easy maintenance.

f) Generator interior of a tight seal for preventing leaks.

g) Maximum diameter of 2.250 inches.

h) Length of 2 meters.

i) System applicable to wells deviated up to 35° (3° for each 100 meters).

j) Withstand harsh environments, with CO₂ and H₂S presence.

k) Primary expander, homogenization chamber and secondary expander manufactured with steal 4140 treated with surface coating with a hardness of 97 RwC.

4) Installation of the enhancer system of flow pattern. The installation of the enhancer system of flow pattern was performed as follows:

The enhancer system of flow is installed on the production piping extreme, it is introduced to the well through a steel line unit by a disgorging tool JDC called davit; after reaching the depth of placement, it anchors the production piping by sudden descendent movements with a mechanical scissors and weight bars, the tightness of the system is obtained by hitting the upper part of the system with blind box. The operation sequence to recover the system is performed by hitting upwards with mechanical scissors and weigh bars to release.

5) The pressure gradient behavior and productions of well Cuitlahuac 802 of Activo Integral Burgos is shown in FIG. 5, which is supplemented with the following results:

a) The enhancer system of flow pattern increased the gas production over 300% compared to the initial production: from 0.315 to 1.08 million cubic feet per day;

b) The well production is continuous and had a steady behavior even during the liquid discharge;

c) It had a remarkable improvement on the flow pattern in the production piping by generating a homogeneous dispersion of both phases, reducing the water shear.

d) It reduced the pressure drops along the production piping (TP), as it was not allowed that the liquid accumulate at the bottom of the well.

e) The deposit energy was preserved due to the increase of bottom pressure flowing, as in the case of operation in the discharge line of high pressure;

f) The anchorage operation of the enhancer system of flow pattern was performed successfully. The response of the well, monitored at the surface with a phase measuring equipment, allowed to observe that the well was stabilized with a gas production higher than normal, due to the application of enhancer system of flow pattern; likewise the liquid production had a more steady behavior, caused by an improvement in the flow pattern.

g) The enhancer system of the flow pattern can be used to extend the flowing life of the wells, as it preserves the deposit energy by reducing the pressure drops along the production piping, same as was identified by the register of flowing bottom pressure taken 2 hours after the installation.

h) It prevents the formation of hydrates, as it increases the temperature in head to 45° C. (113° F.), due to the expansion and heating of gas caused by the enhancer system of flow pattern located at 2,000 m.

i) Additionally, the enhancer system of flow pattern prevents the re-pressure of surface lines because of the accumulation of methane hydrates, which reduce the flow area towards the battery, cause of low gas production especially in winter.

Claims

1. A flow pattern enhancer system for gas wells, comprising the following elements: for displacing the liquids accumulated at the bottom of the well to the surface, taking advantage of the same energy of the gas produced, extending the flowing life of the wells in a continuous form and increasing its recovery factor.

a) primary expander,

b) homogenization chamber,

c) secondary expander,

d) suction veins, and

e) anchorage and tightness system,

2. The flow pattern enhancer system of claim 1, for gas-producing oil wells with liquid load problems.

3. The flow pattern enhancer system of claim 1, where the primary expander has a smaller inner diameter than the homogenization chamber.

4. The flow pattern enhancer system of claim 1, wherein the primary expander is connected to the lower part of the homogenization chamber.

5. The flow pattern enhancer system of claim 1, wherein the homogenization chamber is connected to the primary expander at the lower part and to the secondary expander at the upper part.

6. The flow pattern enhancer system of claim 1, wherein the secondary expander is attached to the homogenization chamber at the upper part of the homogenization chamber.

7. The flow pattern enhancer system of claim 1, wherein the secondary expander houses suction veins.

8. The flow pattern enhancer system of claim 1, wherein the secondary expander at the upper part has a fishing neck.

9. The flow pattern enhancer system of claim 1, wherein said suction veins are housed in low pressure zones inside the secondary expander and communicate the low pressure zones inside the secondary expander with the liquid accumulated outside the system.

10. The flow pattern enhancer system of claim 1, wherein anchorage and tightness systems are coupled in the inside to the primary expander and homogenization chamber, and on the upper extreme to the secondary expander.

11. The flow pattern enhancer system of claim 10, wherein said anchorage and tightness system enables installation of the flow pattern enhancer system at any depth of the production piping of the well.

12. The flow pattern enhancer system of claim 10, wherein the anchorage and tightness system forces the flow to take place only inside the flow pattern enhancer system.

13. The flow pattern enhancer system of claim 10, wherein the anchorage and tightness system has mechanical anchors which are attached to the piping and elastomeric seals which allow the system to anchor and seal the inside in order to perform completely the flow inside the system.

14. The flow pattern enhancer system of claim 1, wherein the flow pattern enhancer system is installed in the lower extreme of the production piping.

15. The flow pattern enhancer system of claim 1, wherein the flow pattern enhancer system can be placed below the depth to which the bubbling pressure is present.

16. The flow pattern enhancer system of claim 1, wherein the gas velocity increases promoting the atomization of liquids, with a relatively high gas flow velocity of 4-6 m/s, achieving fog flow and a continuous flow structure having liquid droplets dispersed in the continuous gas phase.

17. The flow pattern enhancer system of claim 1, wherein the calculations for each element design consider three different process: expansion, compression and mixing, and are performed through specific methods consisting primarily on determining the flow areas and geometries thereof.

18. The flow pattern enhancer system of claim 1, where the drag coefficient is determined by the formula:

Drag coefficient=Driving flow/Dragged flow.

19. The flow pattern enhancer system of claim 1, wherein said flow pattern enhancer system increased gas production over 300% from the initial production.

20. The flow pattern enhancer system of claim 1, wherein the flow pattern enhancer system prevents formation of hydrates.

21. The flow pattern enhancer system of claim 1, wherein said flow pattern enhancer system avoids the re-pressure of surface lines because of methane hydrate accumulation.

22. A method for enhancing the flow of a gas-producing oil well with liquid load problems, which comprises passing a gas stream from the well in sequence through such that gas velocity increases to 4-6 m/s, achieving fog flow with liquid drops dispersed in the continuous gas phase.

a) a primary expander;

b) a homogenization chamber,

c) a secondary expander, and

d) suction veins

23. A gas-producing oil well pipe string arrangement having a flow pattern enhancer system connected in and communicating with the lower portion of said pipe string arrangement, said flow pattern enhancer system comprising the following elements: for displacing liquids accumulated at the bottom of the well to the surface and extending the flowing life of the wells and increasing the recovery factor.

a) primary expander;

b) homogenization chamber,

c) secondary expander,

d) suction veins, and

e) anchorage and tightness system