Flow density tool

Abstract

A flow density tool having a flow housing with an inflow orifice and outflow window and a sensor tube inserted from an end opposite inflow orifice. Two symmetrically placed nuclear sources are covered with a lead blanket from the outside so that the sensors are exposed only to the given source and covered by the same blanket from outside or external radiation to allow the flow density of a continuous flow of discreet media to be measured.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims the benefit of U.S. Provisional Patent Application No. 60/870,306, filed Dec. 15, 2006, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a method and apparatus for logging discreet media flow density, for example as on drilling rig during drilling the subsurface stratas.

BACKGROUND OF THE INVENTION

During drilling of sub-surface formations, drilling mud is circulated down the hole to flow up the drill bit cuttings. The cuttings are separated from the mud and then may be directed to an apparatus for further processing and measurements, for example as described by the author in U.S. Pat. No. 6,386,026 “Cuttings Sample Catcher and Method of Use” and additionally disclosed in U.S. patent application Ser. No. 10/711,333 “Drilling Cutting Analyzer System and Methods of Applications” (Published US 2005-0082468).

It is, therefore, desirable to provide an improved method and apparatus for logging flow density.

SUMMARY OF THE INVENTION

It is an object of the present invention to obviate or mitigate at least one disadvantage of previous flow density meters.

The method and apparatus disclosed here is the new Flow Density Tool using sensors, such as Gamma Ray and Neutron sensors for Logging Flow Density of mud with drill cuttings in return flow, while drilling and other discreet media materials. Neutron sensors may provide, among other things, an assessment or measurement of the porosity of the media flowing through the apparatus. The flow density tool provides a configuration and two (2) or more sensors which in combination provide measurement of the flow density of the discreet media moving through the apparatus (for example drilling mud or fluid containing drill cuttings or drill cuttings).

In a first aspect, the present invention provides a flow density tool for measuring the density of drilling mud containing drill cuttings, including a gamma ray source for directing gamma rays through at least a portion of the drilling mud containing drill cuttings, a gamma ray sensor for detecting the gamma rays, and a flow housing for directing the flow of the drilling mud containing drill cuttings past the gamma ray sensor.

Preferably the flow density tool further includes a neutron source for directing neutrons through at least a portion of the drilling mud containing drill cuttings, and a neutron sensor for detecting neutrons.

Preferably, the gamma ray sensor and the neutron sensor are housed in a sensor tube. Preferably, the flow housing is an elongate tubular having a first end and a second end, an inflow orifice adapted to receive the drilling fluid containing drill cuttings proximate the first end. Preferably, the sensor tube is received in the second end, forming an annular gap between the sensor tube and the flow housing.

Preferably an outflow window is adapted to discharge the drilling fluid containing drill cuttings from the annular gap. Preferably the annular gap is between about 0.5 inch (13 mm) and about 0.75 inch (19 mm). Preferably the flow housing having an upper portion and a lower portion, the outflow window formed in the lower portion. Preferably the gamma ray source is americium 241. Preferably the neutron source is americium 241 upon a beryllium target.

In a further aspect, the present invention provides a method of calculating the bulk density of drilling fluid containing drill cuttings including directing gamma rays through at least a portion of the drilling mud containing drill cuttings and measuring gamma rays, measuring neutron emissions from the drilling fluid containing drill cuttings, and calculating a bulk density based on the gamma rays measured and neutrons measured.

Preferably, the measurement of gamma rays and neutrons measured are synchronized in time.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the attached figure, wherein:

FIG. 1 is a cross-section view of a flow density tool of the present invention.

DETAILED DESCRIPTION

Generally, the present invention provides a method and system for measuring or logging the flow density of a fluid slurry, such as drilling mud (drilling fluid) containing drill cuttings.

Referring to FIG. 1, the flow density tool 20 includes a tubular, such as a pipe 30 with an inflow orifice 7 and an outflow window 8 and a sensor holder tube 9 inserted from the opposite side from the inflow orifice 7 within a flow housing 4. Drilling fluid containing discrete media 10 are received in the inflow orifice 7.

A small nuclear source or sources 5 are covered with a lead blanket 1 or other shielding from the outside so that the sensors are exposed only to the given source and covered by the same other shielding or lead blanket 1 from outside (or external or background) radiation.

The two sensors are preferably a Gamma Ray detector/sensor 2 and a Neutron detector/sensor 3 similar to conventionally used in logging optionally, with some changes that will enhance the signal measurements, such as low temperature operation. The drilling fluid with the drill cuttings flows through the inflow orifice 7 past the sensors 2 and 3 and the gamma ray absorption by the media is measured synchronously as the neutron count is measured to provide a signal or other indication usable by one skilled in the art to determine the gamma ray absorption and neutron count for determination of bulk density of the drilling fluid containing drill cuttings.

Other parameters may be obtained from this apparatus with additional interpretation in combination with the other parameters measured by surface logging while drilling (SLWD) as described in U.S. Pat. No. 6,386,026, and U.S. patent application Ser. No. 10/711,333 mentioned above (Published US 2005-0082468), both of which are incorporated herein by reference.

The apparatus of the present invention is preferably situated before the mini shaker (for example disclosed in U.S. Pat. No. 6,386,026) and the cuttings are pumped with the mud pump through the mud flow house into the flow density tool 20.

The apparatus is preferably connected to the mud flow house (e.g. inflow orifice 7 receives drilling fluid containing cuttings from the mud flow house) and the outflow window 8, preferably at or proximate the bottom of the flow density tool 20 discharges drilling fluid containing cuttings to the feeder.

The sensor holder tube 9 may be suspended by the sensor holder 40 at a spacing of about 0.5 inch (13 mm) to about 0.75 inch (19 mm) between the sensor holder tube 9 and the bottom of the flow housing 4 and inserted from the opposite side from the inflow orifice 7. Preferably, two or more sources 5 of gamma rays, such as Am 241 may be placed from outside of the tool flow housing 4 for creating a gamma ray flow through the discreet media 10. As shown, two sources 5 may be placed in the lower portion of the flow housing 4 so that they are within the drilling fluid containing cuttings. To increase signal, additional sources 5 may be placed a distance from the first two sources 5.

These small nuclear sources 5 are covered with a lead blanket 1 or other shielding from the outside so that the sensors 2 and 3 are exposed only to the given source and covered by the same lead blanket 1 from outside radiation. A resistivity sensor 6 may optionally be placed in the flow density tool 20 to further improve the accuracy of the bulk density determination.

A small neutron source 50 may provide a stream of neutrons into the drilling fluid with drill cuttings. As an example, the small neutron source 50 may include a Americium 241 source directed upon a Beryllium film, or plutonium, or other neutron source. A shield, such as water bath 60 or other shielding covers the neutron source 50 and neutron sensor 3.

While drilling, an increased density in the drilling fluid flow with drill cuttings may indicate the potential caving in of the well bore and a decreased density may indicate a plug generating in the well by deficient hydraulic properties of drilling fluid in the well.

Other parameters may be obtained from this apparatus, such as resistivity sensor 6 with additional interpretation in combination with the other parameters measured by surface logging while drilling (SLWD) as described in U.S. Pat. No. 6,386,026 (Sample Catcher), and U.S. patent application Ser. No. 10/711,333 mentioned above.

As used herein, and as known to one skilled in the art, drilling mud and drilling fluid are used interchangeably.

In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments of the invention. However, it will be apparent to one skilled in the art that these specific details are not required in order to practice the invention.

The above-described embodiments of the invention are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

Claims

1. A flow density tool for measuring the density of drilling mud containing drill cuttings, comprising:

a. a gamma ray source for directing gamma rays through at least a portion of the drilling mud containing drill cuttings;

b. a gamma ray sensor for detecting the gamma rays; and

c. a flow housing for directing the flow of the drilling mud containing drill cuttings past the gamma ray sensor.

2. The flow density tool of claim 1, further comprising

a. a neutron source for directing neutrons through at least a portion of the drilling mud containing drill cuttings; and

b. a neutron sensor for detecting neutron emissions.

3. The flow density tool of claim 2, wherein the gamma ray sensor and the neutron sensor are housed in a sensor tube.

4. The flow density tool of claim 2, wherein the flow housing is an elongate tubular having a first end and a second end, an inflow orifice adapted to receive the drilling fluid containing drill cuttings proximate the first end.

5. The flow density tool of claim 4, wherein the sensor tube is received in the second end, forming an annular gap between the sensor tube and the flow housing.

6. The flow density tool of claim 5, wherein an outflow window is adapted to discharge the drilling fluid containing drill cuttings from the annular gap.

7. The flow density tool of claim 6, wherein the annular gap is between about 0.5 inch (13 mm) and about 0.75 inch (19 mm).

8. The flow density tool of claim 6, the flow housing having an upper portion and a lower portion, the outflow window formed in the lower portion.

9. The flow density tool of claim 1, wherein the gamma ray source is americium 241.

10. The flow density tool of claim 2, wherein the neutron source is americium 241 upon a beryllium target.

11. A method of calculating the bulk density of drilling fluid containing drill cuttings, comprising:

a. directing gamma rays through at least a portion of the drilling mud containing drill cuttings and measuring gamma rays;

b. measuring neutron emissions from the drilling fluid containing drill cuttings; and

c. calculating a bulk density based on the gamma rays measured and neutrons measured.

12. The method of claim 11, wherein the measurement of gamma rays and neutrons measured are synchronized in time.