Wellbore Stability Study Of Silurian Formation In Shun 9 Block

Shuntuoguole Block of Northwest Oilfield,which located Shuntuoguole low uplift in the Tarim Basin,South connected Katake Uplift and Guchengxu Uplift,north-eastern neighbor with Manjiaer Sag,is favorable point area of long-term oil and gas migration from the Northern Shuntuoguole area and Eastern Manjiaer Sag.Shun9 Well obtain low yield oil flow in the Silurian Kalpintag Formation by the large-scale sand fracturing,which achieving a new breakthrough in clastic rock exploration.However,the stability of the upper reservoir stratum of is poor,which seriously threaten the safety of drilling operation and the exploration development process.Questions aimed at complex stratum lithology of silurian in Shun9 Well Block,unclear of rock mechanics and ground stress characteristics,misunderstood of wall collapse mechanism,engineering measures lacking pertinence,this paper based on the data of geology,drilling,logging and core in Shun9 Well Block,through analysising the core characteristics of silurian and sophisticated statistical analysis,to further clarify the characteristics of silurian well-bore instability.To carry out the silurian rock mechanical parameters and stress tests in laboratory,fitting silurian rock mechanics for fetching model parameters and tectonic stress coefficient,to establish the silurian rock mechanical parameters and stress profile,get the parameters of rock mechanics and the law of stress distribution;Analysis of the influence of drilling fluid density,drilling fluid system and well trajectory on borehole collapse,clear the main reasons of the well-bore instability in the silurian strata.Considering the distribution of stresses around the deviated well,characteristics of shale hydration strength and feature of bedding weak surface,establishment of the well-bore collapse pressure calculation model which apply to the characteristics of silurian formation.By using these data of drilled wells in Shun9 Well Block,the calculated results are in good agreement with the field application.The model calculation results can meet the engineering requirements.Combination of silurian strata rock mechanics parameters and stress distribution,activity analysis of drilling fluid and formation collapse pressure calculation,from a range of horizontal well optimization,reasonable density of drilling fluid,the system of drilling fluid and optimization of drilling fluid performance,the optimizated suggestions of silurian strata drilling engineering measures in Shun9 Well Block is proposed.Adoption of this study,we form a way of rock mechanics parameters and stress calculating which suitable for silurian strata in Shun9 Well Block,establish the suitable calculation model of well-bore stability of the silurian strata,propose technical measures for drilling engineering,it provides a theoretical reference and guidance for the later wells deployment,drilling design and optimizated construction measures,drilling fluid system and drilling fluid density,selection of a directional wells direction.