Design method for property parameters of anti-collapse drilling fluid for fractured formations

Abstract

The invention discloses a design method for property parameters of anti-collapse drilling fluid for fractured formations. According to sequence, the design method includes the following steps: core samples are prepared; four of the core samples are chosen for a triaxial compression test and an acoustic emission test, and the crustal stress of a formation owning the core samples is determined; two of the core samples are chosen for the triaxial compression test, and the cohesion and internal friction angle of the weak planes of the rocks are tested; eight of the core samples are chosen to be put into the drilling fluid, the triaxial compression test is carried out after the core samples are soaked for different times, and the cohesion and internal friction angle of the weak planes of the rocks are tested; the cohesion and internal friction angle of the weak planes of the rocks are respectively linearly fitted to soaking times; the fluid-solid coupling theory is utilized to create a fractured formation well surrounding rock stress distribution model; the elastic mechanics coordinate transformation theory is utilized to create a fractured formation weak plane destruction model; a relation chart between the property parameters of the drilling fluid is determined. The design method disclosed by the invention can quantitatively optimize the key property parameters of the drilling fluid according the requirement of a site for well wall stability.

Description

technical field [0001] The invention belongs to the technical field of oil and gas drilling engineering, and relates to a design method of performance parameters of drilling fluid, in particular to a design method of performance parameters of drilling fluid for preventing collapse of fractured formations. Background technique [0002] In recent years, when drilling in fractured formations in many oil and gas fields at home and abroad, complex accidents such as well wall collapse and block loss, well diameter expansion, lost circulation, stuck pipe, buried downhole drilling tools and electrical measuring instruments have often occurred, resulting in extended drilling cycles. The increase in drilling costs has seriously hindered the exploration and development of oil and gas. The remarkable feature of fractured strata is that micro-fractures (weak faces of rocks) are commonly developed. On the one hand, the existence of micro-fractures itself will reduce the mechanical streng...

AI Technical Summary

Problems solved by technology

This design method mainly starts with qualitative evaluation and improvement of drilling fluid performance, does not involve the mechanical model of wellbore stability, does not consider the influence of drilling fluid on the mechanical properties and stress distribution of rock around the well, and does not establish the relationship between the key performance parameters of drilling fluid and the well. Therefore, it is urgent to develop a design method based on rock mechanics for anti-collapse drilling fluid performance parameters in fractured formations to meet the requirements of wellbore stability. requirements

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