Measuring inter-reservoir cross flow rate through unintended leaks in zonal isolation cement sheaths in offset wells

Patent metadata

Field	Value
Publication number	US-2016208599-A1
Application number	US-201514601769-A
Country	US
Kind code	A1
Filing date	Jan 21, 2015
Priority date	Jan 21, 2015
Publication date	Jul 21, 2016
Grant date	—

Abstract

Crossflow between two adjacent reservoir layers through leaky cement sheaths in offset wells during transient-pressure tests in one of the two reservoir layers is diagnosed and quantified. The obtained measures are determined based on individual well and layer properties. The pressure drawdown in the reservoir layer in which pressure transient testing is being performed is measured as a function of time. The longitudinal conductivity of a leaky cement sheath in an offset well and the pressure drawdown in the tested reservoir layer simultaneously control the crossflow rate to the tested reservoir layer from the adjacent reservoir layer at a given time.

First claim

What is claimed is:

1 . A computer implemented method of determining a measure of inter-reservoir crossflow rate to a tested layer of a subsurface reservoir through leaks in cement sheaths of offset wells in the tested layer during a pressure transient test of the tested layer, the computer implemented method comprising the steps of:
obtaining a test measure of well pressure during the pressure transient test on the tested layer; determining a test pressure derivative of the test well pressure at sampled instants of measurement during the pressure transient test of the tested layer; receiving estimated values of conductivity of the cement sheaths of the offset wells; determining a model wellbore flowing pressure at the layer based on the test measure of well pressure and the estimated values of conductivity of the cement sheaths of the offset wells; determining a model pressure derivative based on the test pressure and the estimated values of conductivity of the cement sheaths of the offset wells; determining a model inter-reservoir crossflow rates in the offset wells to the tested layer based on the estimated values of conductivity of the cement sheaths of the offset wells; comparing the model wellbore flowing pressure with the test measure of well pressure; comparing the model pressure derivative with the test pressure derivative; and if the estimated measures and test measures match within an acceptable degree of agreement, storing the estimated values of conductivity of the cement sheaths of the offset wells, the model inter-reservoir crossflow to the tested layer, the model wellbore flowing pressure, and the model pressure derivative; and, if not, adjusting the values of conductivity of the cement sheaths of the offset wells, and repeating the steps of determining a model wellbore flow pressure, determining a model pressure derivative, determining a model inter-reservoir crossflow rates in the offset wells to the tested layer and comparing based on the adjusted values of conductivity of the cement sheaths of the offset wells.

2 . The computer implemented method of claim 1 , further including the step of forming an output display of the stored inter-reservoir crossflow rate to the tested layer.

3 . The computer implemented method of claim 1 , further including the step of forming an output display of the stored estimated values of conductivity of the cement sheaths of the offset wells.

4 . The computer implemented method of claim 1 , further including the step of forming an output display of the stored model wellbore flowing pressure.

5 . The computer implemented method of claim 1 , further including the step of forming an output display of the stored model pressure derivative.

6 . The computer implemented method of claim 1 , wherein the pressure transient testing is performed during well drawdown.

7 . The computer implemented method of claim 1 , wherein the pressure transient testing is performed during well buildup.

8 . A data processing system for determining a measure of inter-reservoir crossflow rate to a tested layer of a subsurface reservoir through leaks in cement sheaths of offset wells in the tested layer during a pressure transient test of the tested layer, the data processing system comprising:
a processor performing the steps of: obtaining a test measure of well pressure during the pressure transient test of the tested layer; determining a test pressure derivative of the test well pressure at sampled instants of measurement during the pressure transient test of the tested layer; receiving estimated values of conductivity of the cement sheaths of the offset wells; determining a model wellbore flowing pressure of the formation layers based on the test measure of well pressure and the estimated values of conductivity of the cement sheaths of the offset wells; determining a model pressure derivative based on the test pressure and the estimated values of conductivity of the cement sheaths of the offset wells; determining a model inter-reservoir crossflow rate to the tested layer based on the estimated values of conductivity of the cement sheaths of the offset wells; comparing the model wellbore flowing pressure with the test measure of well pressure; comparing the model pressure derivative with the test pressure derivative; and if the estimated measures and test measures match within an acceptable degree of agreement, storing the estimated values of conductivity of the cement sheaths of the offset wells, the model inter-reservoir crossflow to the tested layer, the model wellbore flowing pressure, and the model pressure derivative; and, if not, adjusting the values of conductivity of the cement sheaths of the offset wells, and repeating the steps of determining a model wellbore flow pressure, determining a model pressure derivative, determining a model inter-reservoir crossflow rate to the tested well and comparing based on the adjusted values of conductivity of the cement sheaths of the offset wells; and a memory storing the estimated values of conductivity of the cement sheaths of the offset wells, the model inter-reservoir crossflow to the tested layer, the model wellbore flowing pressure, and the model pressure derivative.

9 . The data processing system of claim 8 , further including:
an output display forming an output record of the stored model inter-reservoir crossflow to the tested layer.

10 . The data processing system of claim 8 , further including:
the output display forming an output record of the stored measure of the estimated values of conductivity of the cement sheaths of the offset wells.

11 . The data processing system of claim 9 , further including:
the output display forming an output record of the stored model pressure derivative.

12 . The data processing system of claim 8 , further including:
the output display forming an output record of the stored model wellbore flowing pressure.

13 . A data storage device having stored in a non-transitory computer readable medium computer operable instructions for causing a data processing system to determine a measure of inter-reservoir crossflow rate to a tested layer of a subsurface reservoir during a pressure transient test of the tested layer, the instructions stored in the data storage device causing the data processing system to perform the following steps:
obtaining a test measure of well pressure during the pressure transient test of the tested layer; determining a test pressure derivative of the test well pressure at sampled instants of measurement during the pressure transient test of the tested layer; receiving estimated values of conductivity of the cement sheaths of the offset wells; determining a model wellbore flowing pressure of the formation layers based on the test measure of well pressure and the estimated values of conductivity of the cement sheaths of the offset wells; determining a model pressure derivative based on the test pressure derivative and the estimated values of conductivity of the cement sheaths of the offset wells; determining a model inter-reservoir crossflow rate to the tested layer based on the estimated values of conductivity of the cement sheaths of the offset wells; comparing the model wellbore flowing pressure with the test measure of well pressure; comparing the model pressure derivative with the test pressure derivative; and if the estimated measures and test measures match within an acceptable degree of agreement, storing the estimated values of conductivity of the cement sheaths of the offset wells, the model inter-reservoir crossflow to the tested layer, the model wellbor

Assignees

• Saudi Arabian Oil Co

Inventors

• Rahman Noor M Anisur
• Nooruddin Hasan A

Classifications

• 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

• E21B47/06 Primary

  Measuring temperature or pressure · CPC title

• G01V99/00

  Subject matter not provided for in other groups of this subclass · CPC title

• E21B47/005

  Monitoring or checking of cementation quality or level · CPC title