Optimization Of Horizontal Well Bore Structure In Jinlong 2 Well Block

Jinlong 2 well area is the key productivity construction block of Xinjiang Oil Field Company.Due to complex geological conditions and unclear understanding of block pressure system at the beginning,well leakage and well collapse accidents occur frequently,complex original well structure and unreasonable depth of casing in the block,which results in large casing consumption and long construction period in Jinlong 2 well area,which seriously restricts oil and gas exploration and development in this block.Therefore,this thesis clarifies the mechanism of wall destabilization in the third section of Wuerhe,studies the influence of drilling fluid parameters on wall stability,establishes a collapse cycle model,calculates the three pressure profiles in Jinlong 2 well area,and puts forward the optimization schemes of casing program of horizontal wells in Upper Wuerhe Formation reservoir and Jiamuhe Formation reservoir in Jinlong 2 well area.The main research results are as follows:(1)Through drilling fluid immersion test of mudstone in the third section of Wuerhe Formation,the mechanism of mudstone wall destabilization in the third section of Wuerhe Formation is explored and collapse period is predicted.At the same time,the solid-liquid two-phase flow model of drilling fluid was established and the influence of drilling fluid parameters on mud cake formation speed and quality was studied.The results show that the wall instability of the third section of Wuerhe is caused by mudstone hydration damage.Considering the requirement of drilling speed,low viscous drilling fluids should be used to optimize the solid particles matching the pore size of formation,improve the density of drilling fluids,help to form high-quality mud cakes in a short time and reduce the filtration of drilling fluids,thus alleviating wall collapse caused by mudstone hydration damage.(2)The causes of abnormal high pressure formation in Jinlong 2 well area are analyzed,the calculation criteria of rock strength are determined,and the calculation methods of formation pore pressure,fracture pressure and collapse pressure are optimized according to the formation characteristics of the block.The three pressure profiles in Jinlong 2 well area are calculated to support the optimization of well structure.The calculation results show that the compaction above 2000 m is basically normal and there is abnormal high pressure below 2000 m.The formation fracturing pressure coefficient from Upper Karamay Formation to Jiamuhe Formation in Jinlong 2well area has little change,and the collapse pressure of Wusan Formation is high,so the drilling fluid density should be properly increased.(3)Horizontal well structure of Upper Uerhe Formation reservoir and Jiamuhe Formation reservoir is optimized.Horizontal wells of Upper Uerhe Formation reservoir are optimized from four to three openings.Horizontal wells of Jiamuhe Formation reservoir are optimized from the bottom of Baijiantan to the middle of Lower Karamay Formation.The depth of three open casing is optimized from the bottom of Upper Uerhe Formation to point A.Meanwhile,a drilling fluid performance optimization scheme of Upper Uerhe Group Wusan Formation is proposed.At present,the optimized casing program provides technical support for comprehensive speed-up in Jinlong 2well area,shortens drilling cycle,basically avoids well collapse accidents,reduces well leakage accidents and reduces non-drilling time.At the same time,the casing program structure will provide guidance and reference for drilling in deep Permian and Carboniferous of the basin.