Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Earth science
Reexamination Certificate
2001-06-05
2003-08-19
McElheny, Jr., Donald E. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Earth science
Reexamination Certificate
active
06609067
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to methods for predicting and maintaining wellbore stability during drilling, well servicing and production in subterranean formations, particularly hydrocarbon bearing subterranean formations.
2. Description of Relevant Art
As used herein, the term “(in)stability” shall be understood to mean “stability or instability.” Wellbore (in)stability in shales is a major problem costing the petroleum industry, according to conservative estimates, $700 million annually. Understanding and modeling mechanisms of shale (in)stability is an ongoing industry effort. Drilling a hole into a formation in equilibrium induces stress concentration in the vicinity of the borehole. Interactions will occur if parameters such as chemical potential, electrical potential, thermal potential, ionic concentration, etc., of the drilling fluid and the shale formation fluid are not in equilibrium. Any differences in these parameters will alter the near wellbore pore pressure which in turn will influence the borehole equivalent stress-state and the shale mechanical strength thus affecting wellbore (in)stability. Tests conducted at compressive uniaxial and triaxial stress conditions in the past have indicated the strong influence of these parameters on shale strength.
Wellbore instability predominantly occurs in chemically reactive shales that overlay reservoirs. A major concern of the drilling engineer is either keeping the borehole wall from collapsing (packing oft) or fracturing (losing circulation).
Past efforts to develop improved well bore models (“WBM”) for shale drilling have been hampered by a limited understanding of the drilling fluid/shale interaction phenomenon. This limited understanding has resulted in drilling fluids being designed with properties inadequately or insufficiently optimized to prevent the onset of borehole (in)stability problems. Historically, wellbore (in)stability problems have been approached on a trial-and-error basis, going through a costly multi-well learning curve before arriving at reasonable solutions for optimized operations and systems.
Recent studies of fluid-shale interactions have produced fresh insights into the underlying causes of borehole (in)stability; and chemical potential related instabilities in shales have been identified. A chemical potential borehole stability model, derived for an arbitrary borehole orientation, has been successfully implemented to address borehole (in)stabilities. This model, based on a well-established elastic modeling approach, is discussed in Tare, U. A., and Mody, F. K.: “Novel Approach to Borehole Stability Modeling for ERD and Deepwater Drilling”, paper SPE 52188, 1999 SPE Mid-Continent Operations Symposium, Oklahoma City, USA, Mar. 28-31, 1999, incorporated herein by reference.
Advances in technology are providing wider and greater capabilities for new, more reliable, accurate and rugged downhole sensors and tools. Such apparatuses and sensors are increasingly able to collect and transmit information to the surface as it is happening.
With increasing economic demands on reducing rig downtimes associated with borehole instability problems, there is increasing need for the ability to predict and resolve instabilities in the field using MWD/LWD (measuring while drilling/logging while drilling) data in conjunction with prior geophysical and shale/fluid interaction knowledge. However, previous attempts have focused on earth stresses, using drilling data and borehole (in)stability modeling on a “post-mortem” basis, i.e., after substantial problems have occurred. There is a need for methods that enable instability problems to be avoided.
SUMMARY OF THE INVENTION
A method is disclosed for maintaining subterranean formation stability, and particularly wellbore stability during drilling, well completion and servicing operations, and even during production and enhanced recovery operations. The method of the invention affords maintenance of wellbore stability throughout the life of a well penetrating a subterranean formation. Moreover, the method provides for real-time monitoring of fluid-formation interaction such that adjustments can be made before (in)stability problems occur.
In the method, initial formation characteristics or parameters are estimated or obtained and the rock strength of the formation is estimated. Characteristics of the fluids injected into the wellbore or the formation during drilling, or during well completion and servicing operations, or during production or enhanced recovery operations, are also estimated or obtained. This data concerning the formation and the fluids is input into a well-stability model and results are used to revise the estimates of the formation parameters and/or the fluid parameters or to adjust the fluid composition or characteristics. These parameters and the model results are updated with real time formation measurements taken during the particular operation being conducted (i.e., drilling, well servicing, or production). Continued acquisition and processing of the formation data in the model allows the fluids to be adjusted as needed to avoid formation instability problems caused by interaction of the fluids with the formation.
REFERENCES:
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Mody, F. K. and Hale, A.H.: “A Borehole Stability Model to Couple the Mechanics and Chemistry of Drilling Fluid Shale Interaction”, papr SPE/IADC 25728, presented at the 1993 SPE/IADC Drilling Conference held in Amsterdam, Feb. 23-25 1993, pp. 473-490.
Tare, U.A., Mese, A. I., and Mody, F. K.: “Interpretation and Application of Acoustic and Transient Pressure Response to Enhance Shale (In) Stabiity Predictions”, paper SPE 63052, presented at the 2000 SPE Annual Technical Conference and Exhibition in Dallas, Texas, Oct. 1-4, 2000, pp. 1-9.
Tare, U. A. and Mody, F. K.: “Novel Approach to Borehole Stability Modeling for ERD and Deepwater Drilling”, paper SPE 52188, 1999 SPE Mid-Continent Operations Symposium, Oklahoma City, USA Mar. 28-31, 1999, pp. 1-9.
Tan, C. P., Rahman, S. S., Richards, B. G., and Mody, F. K.: “Integrated Rock Mechanics and Drilling Fluid Design Approach to Manage Shale Instability”, paper SPE 47259, SPE/ISRM Eurock '98, Trondheim, Norway, Jul. 8-10, 1998, pp. 291-300.
Ghassemi, A., Diek, A., and Roegiers, J. C.: “A Solution for Stress Distribtuion Around an Inclined Borehole in Shale”, paper No. 043, Int. J. Rock Mech. Min. Sci., vol. 35 No. 4/5. p. 538-540, 1998.
Staverman, A. J.: “Theory of Measurement of Osmotic Pressure”, Recueil des Travaux Chimiques des Pays-Bas, v. 70, pp 344-352, (1951).
Bradley, W. B.: “Failure of Inclined Boreholes”, J. Energy Res. Tech. (Dec. 1979) 232: Trans., AIME, 101, pp. 1-9.
Mody, F. K., Tare, U. A., and Kirsner, J.: “Silicate-Based Drilling FLuids—A Unique High Membrane Efficient WBM that Provides Shale Protection Mechanism”, paper PP# N128 Colaper XI—Argentina 98, XI Congresso Lationamericano De Perforacion, Buenos Aires, Argentina, Oct. 98.
Y. Abousleiman;, S. Ekbote; L. Cui; F. Mody; J.C. Roegiers; and M. Zaman; Time-Dependent Coupled Processes in Wellbore Design and Stability, SPE 56759; presented at the 1999 SPE Annual Technical Conference and Exhibition held in Houston, Texas Oct. 3-6, 1999.
Hakimuddin Mustafa
Jiao Di
Mese Ali I.
Mody Fersheed Khodadad
Tare Uday Arun
Halliburton Energy Service,s Inc.
McElheny Jr. Donald E.
Roddy Craig W.
Tripp Karen B.
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