Method for characterizing subsurface formations using fluid pressure response during drilling operations

Patent metadata

Field	Value
Publication number	US-9328574-B2
Application number	US-201213415952-A
Country	US
Kind code	B2
Filing date	Mar 9, 2012
Priority date	Mar 9, 2011
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

A method for characterizing a subsurface formation using a fluid pressure response during wellbore drilling operations includes the steps of determining a change in wellbore pressure proximate the surface, calculating a change in volumetric flow rate out of the wellbore as a function of the change in wellbore pressure proximate the surface, determining a downhole fluid pressure in the wellbore corresponding to the change in wellbore pressure proximate the surface and determining a productivity index value as a function of the change in volumetric flow rate, the downhole fluid pressure and a reservoir pressure.

First claim

What is claimed is:

1. A method comprising:
characterizing a subsurface formation using a fluid pressure response during wellbore drilling operations, wherein characterizing the subsurface formation comprises:
determining a change in volumetric flow rate out of the wellbore and determining a downhole fluid pressure in the wellbore while inducing a change in wellbore pressure proximate a surface of the Earth by lowering an annulus pressure during drilling;
determining a productivity index value as a function of the determined change in volumetric flow rate, the determined downhole fluid pressure, and a reservoir pressure; and
calculating, after determining the productivity index value, a subsequent change in volumetric flow rate out of the wellbore as a function of the productivity index value, the reservoir pressure, and another downhole fluid pressure determined during drilling.

2. The method of claim 1 further comprising the step of: formulating volumetric flow rate out of the wellbore as a function of the wellbore pressure proximate the surface.

3. The method of claim 1 wherein at least one of the downhole fluid pressure or the another downhole fluid pressure is determined by using a PWD sensor proximate a bottom end portion of a drill string.

4. The method of claim 1 wherein at least one of the downhole fluid pressure or the another downhole fluid pressure is determined by modeling.

5. The method of claim 1 wherein the reservoir pressure is estimated through a fingerprinting process.

6. The method of claim 1 wherein the reservoir pressure is estimated through a dynamic leak off test.

7. The method of claim 1 further comprising the steps of: calculating another change in volumetric flow rate from the wellbore as a function of at least the productivity index value.

8. The method of claim 1 wherein the step of determining a change in volumetric flow rate out of the wellbore as a function of the change in wellbore pressure proximate the surface includes the steps of:
pumping fluid into the wellbore from a surface location at various volumetric flow rates, the pumping step occurring when no formation fluid is flowing into the wellbore such that the volumetric flow rate of fluid being pumped into the wellbore approximates the volumetric flow rate of fluid flowing out of the wellbore;
measuring wellbore pressure proximate the surface corresponding to each of the various flow rates; and
formulating the volumetric flow rate out of the wellbore as a function of the wellbore pressure proximate the surface.

9. The method of claim 1 further comprising the step of: repeating all of the steps upon drilling into a new formation.

10. A method for calculating flow rate of fluid flowing from a wellbore based upon a fluid pressure response during wellbore drilling operations, the method comprising:
pumping fluid into a balanced wellbore from a surface location at various volumetric flow rates during drilling, the pumping step occurring when little or no formation fluid is flowing into the wellbore such that volumetric flow rate of fluid being pumped into the wellbore approximates the volumetric flow rate of fluid flowing out of the wellbore;
measuring wellbore pressure proximate a surface of the Earth corresponding to each of the various volumetric flow rates during drilling;
determining an equation for calculating the approximated volumetric flow rate out of the wellbore as a function of the measured wellbore pressure proximate the surface;
inducing a change in wellbore pressure proximate the surface during drilling;
calculating a change in volumetric flow rate out of the wellbore during drilling as a function of the induced change in wellbore pressure proximate the surface using the determined equation;
determining a downhole fluid pressure in the wellbore corresponding to the induced change in wellbore pressure proximate the surface during drilling;
determining a productivity index value as a function of the change in volumetric flow rate out of the wellbore, the downhole fluid pressure corresponding to the induced change in wellbore pressure proximate the surface, and a reservoir pressure;
monitoring, after determining the productivity index value, for a subsequent change in wellbore pressure proximate the surface during drilling;
determining another downhole fluid pressure when the subsequent change in wellbore pressure is detected during drilling; and
calculating another flow rate out of the wellbore as a function of the productivity index value, the reservoir pressure, and the another downhole fluid pressure during drilling.

11. The method of claim 10 wherein at least one of the downhole fluid pressure or the another downhole fluid pressure is determined by using a PWD sensor proximate a bottom end portion of a drill string.

12. The method of claim 10 wherein at least one of the downhole fluid pressure or the another downhole fluid pressure is determined by modeling.

13. The method of claim 10 wherein the reservoir pressure is estimated through a fingerprinting process.

14. The method of claim 10 wherein the reservoir pressure is estimated through a dynamic leak off test.

15. The method of claim 10 wherein the steps of monitoring for the subsequent change in wellbore pressure proximate the surface, determining another downhole fluid pressure when the subsequent change in wellbore pressure is detected and calculating volumetric flow rate out of the wellbore as a function of the productivity index value, the reservoir pressure, and the another downhole fluid pressure are conducted in real time.

Assignees

• Sehsah Ossama R
• Smith International

Inventors

• Sehsah Ossama R

Classifications

• E21B21/08 Primary

  Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure (valve arrangements therefor E21B21/10) · CPC title

• E21B49/008

  by injection test; by analysing pressure variations in an injection or production test, e.g. for estimating the skin factor (measuring pressure E21B47/06) · CPC title