Abstract
As a difficult problem, sidewall instability has been beset drilling workers all the time. Not only does it cause huge economic losses, but also it determines the success or failure of drilling engineering. Due to complex relationship between various factors which influence sidewall stability, it hasn’t been found a widely applied method to predicate sidewall stability so far. Therefore, in order to formulate corresponding measures to ensure successful drilling, searching for a kind of better method to forecast sidewall stability before drilling becomes an imperative and significant topic for drilling engineering. On the basis of traditional sidewall stability analytical method, we have put forward the Fuzzy Comprehensive Evaluation Method to forecast sidewall stability regulation using physico-chemical performance parameters of the clay mineral. This method has been improved by introducing the Analytic Hierarchy Process (AHP) and the Maximum Subjection Principle in the application process. After introducing Analytic Hierarchy Process to identify weight, and Maximum Subjection Principle to obtain evaluation results, it has reduced the influence of human factors and enhanced the accuracy of the fuzzy evaluation results. The application in Hailaer Area indicates that this method can predict sidewall stability of gas-oil well with high credibility and strong practicability.
Highlights
Sidewall stabilization is a key technology as well as a big problem in the drilling process
Before applying the principle of maximum subjection to deal with the evaluation results, you need to discuss the results, to test the validity of the principle of maximum subjection
We determine the cation exchange capacity CEC, ζ potential, swelling, rolling recoveries, formation water activity and other physico-chemical properties of clay mineral through indoor experiments, and evaluate the mineral swelling and dispersion properties to lay the foundation for sidewall instability mechanism and the development of anti-collapse response
Summary
Sidewall stabilization is a key technology as well as a big problem in the drilling process. Sidewall instability will cause great difficulties to the drilling engineering, such as shrinking diameter, sticking of drilling rod, borehole enlargement and lowering cementing job quality. These accidents extend the drilling cycle, and raise the drilling cost [1,2,3]. From the angle of reducing the drilling cost and speeding up exploration and development of oil and gas, further researching sidewall stability of clay shale has an extremely vital significance. This article elaborates the comprehensive use of analytic hierarchy process and fuzzy comprehensive evaluation method for forecasting sidewall stability which is scientific and reasonable from two aspects of theory and practice
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