Wellbore Stability Studies In Feng Gu And Gao Miao Structure

Fenggu and Gaomiao Structure is one of the target blocks of gas exploration anddevelopment in western Sichuan,and it located in middle section of western Sichuandepression Xiaoquan-Xinchang-Hexing-Fenggu NEE to the inherited uplift in theEast.Previous studies showed that Fenggu and Gaomiao Structure has good prospectof oil and gas exploration and development. Because of the impact of complextectonic movement and sedimentary environmental, Fenggu and Gaomiao Structurehas complex engineering geological characteristics and wellbore stability difference,and it has become a prominent problem in drilling. This paper base on oil and gasfield development geology, structural geology, reservoir engineering, geophysicalwell logging, rock mechanics and engineering, drilling engineering theory and method,and it combines with previous research results,making system analysis of rockmechanics, formation pore pressure, stress, collapse pressure, fracture pressure andother parameters and characteristics, doing a comprehensive study on the wellboremechanical stability,and put forward countermeasures of drilling technology.This paper is in a comprehensive collection of drilling, logging, testing andremoulding of reservoir and other related information, through the experiment andgeophysical logging data combining rock mechanics parameter prediction modelestablishment and profile. It use the Eaton method to establish the formation porepressure prediction model and section, makes clear that pore pressure is verticallydivided into normal pressure zone, the boost of transition zone, the abnormal highpressure zone and step-down zone. It use fracturing data, GMI stress analysisidentified the Fenggu and Gaomiao tectonic stress state belonging to strike-slip stresstype, and use imaging logging data and well logging data to analyze the Xujiaheformation of maximum horizontal stress direction for the near east-west. In apreferred wellbore instability criterion, it establishs the formation collapse pressure,fracture pressure prediction model and the corresponding profile of Fenggu andGaomiao Structure, and it shows that longitudinal Shaximiao-Xujiahe three sectionsformation collapse pressure is higher, it’s prone to occur wellbore instability,and other formation collapse pressure is lower. It also shows that formation fracture pressure ishigher overall, it’s less likely to break formation. At the same time, combinating withdrilling data and the existing drilling technology,it puts forward area drillingtechnology in drilling engineering, design and construction to provide fundamentalbasis.The research results in this paper will service subsequent drilling and completionengineering,and it will reduce the underground engineering status effectively,improvethe drilling efficiency, shorten drilling cycle, reduce drilling cost. It has importantrealistic significance on the realization of Fenggu and Gaomiao Structure of efficientgas exploration and development.