Low-density drilling feasibility fast evaluation method

Abstract

The invention relates to a low-density drilling feasibility fast evaluation method suitable to be used in a petroleum and natural gas development process. According to the method, whether the well wall in the drilling process is stable or not is judged according to the slurry liquid column pressure P in a corresponding wellbore when a critical plastic state is reached. The method comprises the following steps of: obtaining parameters required in a well wall stability prediction model according to complete stress-strain test data of stratum rock and mechanics characteristic parameters of the stratum rock; obtaining the corresponding well wall collapse pressure P<b, critical> when the critical plastic state is reached; and judging whether the slurry liquid column pressure P selected and used in the field is greater than the P<b, critical> or not. If the slurry liquid column pressure P in the well hole is greater than the P< b, critical>, a result shows that the well wall keeps stable; if the P is smaller than the P< b, critical>, a result shows that the well wall loses the stability and can collapse; and if the P is equal to the P< b, critical>, a result shows that the well wall plasticity in the drilling process reaches the critical state. The method is provided on the basis of damage mechanics though being combined with a unified strength failure criterion. Through field practical inspection, the method has good application effects.

Description

technical field [0001] The invention relates to the technical field of well wall stability during drilling in the oil and gas development process, in particular to a fast feasibility evaluation method suitable for low-density drilling. Background technique [0002] Wellbore stability is an important issue in petroleum drilling engineering. According to statistics, countries around the world spend hundreds of millions of dollars in dealing with such problems every year. The instability of the well wall prevents the drilling construction from proceeding smoothly, and causes huge losses to the exploration and development of underground oil resources. Therefore, it is of great significance to start from the mechanical mechanism of wellbore instability, establish a wellbore mechanical model, analyze the influence of in-situ stress, formation pore pressure and rock mechanical parameters on the wellbore stability, and provide a drilling safety mud density design method . [0003...

AI Technical Summary

Problems solved by technology

At present, there is no systematic and effective method for rapid evaluation of the feasibility of low-density drilling, and no wellbore stability prediction model suitable for low-density drilling has been established.

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