Permeability modification and water shut off composition and process

Abstract

A composition and process for reducing the permeability of a matrix without completely blocking the matrix {is describe}. The composition uses a nano-sized water insoluble particle as a template to control the permeability by determining the size of the holes formed in the matrix.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on provisional application Ser. No. 61/518,644, filed on May 5, 2011

FIELD OF INVENTION

The present invention generally relates to compositions and a method of reducing but not eliminating permeability in an otherwise heterogeneously permeable matrix

BACKGROUND OF THE INVENTION

Relative permeability control is essential for all types of water control problems in the oil field. The goal of a relative permeability modifier (RPM) is to reduce the effective permeability to water and increase the oil and/or gas production. This would reduce water-handling problems and lost oil production. Furthermore, the relative permeability modifier can increase the effectiveness of a water flood and other Enhanced Oil Recovery (EOR) processes.

None of the currently applied relative permeability modifier processes or techniques have consistently performed well in field operations.

The present invention of the permeability modifier can be used in subterranean reservoirs to modify the permeability of the high permeability areas. The permeability modifier can also be used in many applications to modify the relative permeability and improve the oil and gas recovery including but not limited to, water shut off, drilling, fracturing, cementing, acidizing, waterflooding, chemical enhanced oil recovery, (CEOR) polymer flooding, CO2 flooding.

LIST OF FIGURES

FIG. 1 shows the structure of the internal phase and the final solid matrix.

BRIEF DESCRIPTION OF THE INVENTION

The present invention involves the use of oil soluble or dispersible nano-sized particles dispersed in a non-aqueous carrier to form a template for providing permeable channels in an otherwise impermeable solid matrix. The permeable solid matrix can be used for water shut off or permeability modification that can reduce the water channeling through fractures, vugs, or reduce the bottom water drive without risk of sealing off the oil bearing pore spaces in a reservoir. The rate of formation of the permeable gel and the permeability can be controlled based on the degree of the shut off required and the degree of penetration into the reservoir. Propagation of a liquid or gas through an enclosed area such as an oilfield reservoir to selectively control the permeability of the area can be controlled. The present invention also includes the use of oil soluble resin or sized CaCO3, NaCl as templates to enable the oil or gas flow after the otherwise impermeable matrix id formed.

DETAIL DESCRIPTION OF THE INVENTION

The composition of the present invention contains:

• • a) a material capable of forming a tight impervious solid matrix precursor,
  • b) a water insoluble, oil soluble or oil dispersible material that can be used as template to create pore spaces in the impervious gel (hydrophobic core),
  • c) a water immiscible carrier for the template (oil),
  • d) a material that can initiate the controlled gellation of the otherwise tight impervious gel (initiator),
  • e) optionally a porous solid material of specific size and distribution to be used as spacer to create channels within the gel,
  • f) one or more emulsifiers, and,
  • g) an aqueous carrier for the solid matrix precursor.

The material capable of forming a tight impervious solid matrix includes but is not limited to sodium silicate. The water insoluble, oil soluble or dispersible material that can be used as a hydrophobic core to create pore spaces in the impervious gel includes but is not limited to, magnesium stearate, calcium stearate, oil soluble resins and/or oil soluble waxes of different particle sizes, inorganic salts and porous nanoparticles. In the case of application to an oilfield reservoir, the size of this material must be small enough to allow for penetration into the reservoir without permanently blocking small channels within the rock.

The water immiscible carrier can be any of a number of suitable carriers including but not limited to crude oil, mineral oil, diesel oil, hydrocarbon solvent, vegetable oils, synthetic and natural fatty esters, and aromatic solvent. The water immiscible carrier is used to suspend the template material and increase the final size of the pore spaces created in the gel. The initiator can be any material that can initiate a chemical reaction that converts the solid matrix precursor to a tight impervious mass. These include but are not limited to various salts, inorganic and organic acids, esters and/or oil soluble acids. The imitator can be included in the internal phase or can be injected separately once all the ingredients are in place by methods known to the art.

The porous solid can be used as a spacer to create channels within the matrix through which liquid can flow or as a medium to contain one or more of the ingredients for slow release from the non-aqueous to the aqueous phase. The porous solid may also serve to introduce other non-aqueous ingredients in the final permeable solid matrix. Porous spheres of various sizes or oil soluble solids can also be used to control the pore size and distribution.

The one or more emulsifiers are used to emulsify or disperse the non-aqueous phase composed of the water immiscible template, the water immiscible carrier and the gel initiator into the aqueous phase.

They can be any of a number of non-ionic, anionic, cationic or amphoteric surfactants that have been found to be suited for such a purpose.

The aqueous carrier can be any of a number of liquids including but not limited to water, seawater, produce brine, synthetic brine.

The time required for the solid permeable matrix to form and the crushing strength is determine by the ratio of solid matrix precursor to water and the amount initiator used. Using more initiator will speed up solid matrix formation. Usually a higher ratio of solid a matrix precursor gives I a stronger matrix.

The permeable solid matrix can be introduced into reservoirs containing channels, erosions, fractures, bottom water, un-wanted gas cap, coning, etc. to partially seal or to reduce the porosity without completely blocking off flow. After the matrix has set deep within the reservoir it can be made permeable by passing oil or brine or water through it to wash out the oil soluble particles dispersed within the gel and/or remove any other entrained material such as oil. In cases where the heat within the reservoir is high enough the oil soluble particles can be melted in situ to form permeable pathway through the gel. If a lipophilic surfactant is added to the aqueous solid matrix precursor before adding the non-aqueous phase the resulting walls of the pores formed can be rendered hydrophobic allowing oil to pass through and rejecting water. FIG. 1 shows the structure of the matrix formed when the internal phase containing the oil, emulsifier, hydrophobic core and the initiator are mixed with the external solution containing the solid precursor.

The invention allows for tunable permeability by allowing for changes in the “holes” formed in the matrix by changing the size of the hydrophobic core and the amount of oil and emulsifier used.

The intent of partially blocking the fractures is to allow subsequent injection fluid to contact the reservoir matrix more evenly so that more oil is contacted and can be recovered from the reservoir. The injection fluid can be water, brine, synthetic brine or seawater and may contain other ingredients commonly included and known to those familiar with the art to recover residual oil from the reservoir. These ingredients include but are not limited to surfactants, viscosifiers, corrosion inhibitors, scale inhibitors, biocides, clay swelling inhibitors, wetting agents.

Example 1

This example demonstrates the effect of different ratios of internal to external phase on the solidification time.

A non-aqueous internal phase is formed by adding 20 grams of PEG 400 dioleate (emulsifier) and 10 grams of ethyl lactate (ester) to 20 grams of crude oil as shown in Table 1. To these, 10 grams of powdered magnesium stearate powder is added and mixed to uniformly disperse the magnesium stearate. In separate containers various amounts of Sodium Silicate Type N available from PQ Corporation are added. The non-aqueous internal phase is then added, mixed and the entire mixture allowed to solidify according to the ratios shown in Table 2 below.

TABLE 1
Internal Phase     Wt %
Crude Oil          40
PEG 400 Dioleate   40
Ethyl Lactate      10
Magnesium Stearate 10
Total              100

	TABLE 2
		A	B	C	D	E
	Internal Phase, wt %	30	20	10	5	2.5
	Type N Sodium Silicate,	70	80	70	95	97.5
	wt %
	Time to Solidify, min	<5	30	120	180	300

Example 2

This example demonstrates the application of the invention to create a uniform porosity in a fracture sand pack. This property is desirable for application such as Water Flooding, Chemical Enhanced Oil Recovery (CEOR), polymer flooding, and any other application where a uniform sweep efficiency is desired or required.

Two 1 inch diameter by 12 in long sand packs were prepared using gravel of collected between a No. 10 and a No 60 Tyler screen. This provided columns having large channels simulation fractures and vugs. One column was left untreated. The second was treated by introducing 1 pore volume of the formulation described in Table 2 column C. After this column and its contents were allow to stand for 2 hours at room temperature both columns were eluted with water containing 0.05% methylene blue. The rate of elution and the time for initial appearance of the blue dye at the outlet of the column for each were recorded as well as the appearance of the material propagating through the column. These observations and measurements are reported in Table 3.

TABLE 3
	Untreated Column	Treated Column
Time for first drops to elute	<30 seconds	3.5 minutes
Flow rate, ml/min	6.4	1.2
Initial time for elution of dye	45 seconds	52 minutes
Appearance	Channeling	Plug Flow

Further embodiments and alternative embodiments of various aspects of the present invention may be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiment. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, as would be apparent to those skilled in the art after having benefited by this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the flowing claims. In addition, it is to be understood that features described herein independently may, in certain embodiments, be combined.

While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

Claims

1. A process for reducing the permeability of a solid matrix by introducing into the reservoir matrix a composition composed of the following allowing the composition to harden creating small pores within the larger channels of the matrix.

a) a material capable of forming a impervious solid matrix precursor,

b) a water insoluble, {oil soluble} or oil dispersible nano-sized material that can be used as template to create pore spaces In the impervious gel,

c) a water immiscible carrier for the template,

d) a material that can initiate the controlled gellation of the tight otherwise impervious gel,

e one or more emulsifiers, and,

f an aqueous carrier for the solid matrix precursor, and,

2. The process for reducing the permeability of a solid matrix described in claim 1 where the material capable of forming a tight impervious solid matrix is silica gel.

3. The process for reducing the permeability of a solid matrix described in claim 1 where the

water insoluble, oil soluble or oil dispersible hydrophobic core is chosen from the group: magnesium stearate, calcium stearate, oil soluble resins, oil soluble waxes of different particle sizes and porous nano particles of different sizes.

4. The process for reducing the permeability of a solid matrix described in claim 1 where the water immiscible carrier is chosen from the group: crude oil, mineral oil, diesel oil, hydrocarbon solvent, vegetable oils, synthetic esters, natural fatty esters, aromatic solvent.

5. The process for reducing the permeability of a solid matrix described in claim 1 where material that can initiate the controlled gelation of the tight impervious gel is chosen from the group: various salts, inorganic acids, organic acids, esters, oil soluble acids.

6. The process for reducing the permeability of a solid matrix described in claim 1 where the material that can initiate the controlled gelation of the tight otherwise impervious gel is added along with the other components described in claim 1 into the pore spaces of the matrix.

7. The process for reducing the permeability of a solid matrix described in claim 1 where the material that can initiate the controlled gellation of the tight otherwise impervious gel is added after the other components described in claim 1 have been introduced to the pore spaces of the matrix.