东海低孔渗地层的钻井液体系优化与应用

东海西湖凹陷区块存在一批大型低孔渗油气田,这些油气田大多埋藏较深,地层岩性均质性差,砂泥岩互层胶结疏松且夹发育煤层,这些地质特征易导致钻井过程中泥岩水化膨胀、剥落掉块以及煤层垮塌等井下复杂情况.PEM钻井液体系是东海西湖凹陷区块广泛应用的成熟体系,使用效果和经济性良好.为满足东海井深日益增加的高温深井的作业需求,减少钻...

Optimization and Application of Drilling Fluid System for Low Porosity and Low Permeability Formation in the East China Sea

There are a number of large low porosity and low permeability oil and gas fields in the Xihu sag of the East China Sea.Most of these oil and gas fields are deeply buried,with poor lithology homogeneity,loose cementation of sand and mudstone interlayer and coal seams developed in the center,which are easy to lead to complicated conditions during drilling such as the hydration expansion of mudstone,peeling blocks and coal seam collapse.PEM drilling fluid system is widely applied in the Xihu sag of the East China Sea,with good application effect and economy.In order to meet the requirements of high temperature deep wells with increasing depth in the East China Sea,reduce drilling complicated conditions,and better protect low porosity and low permeability oil and gas reservoirs,through experimental research,the high temperature stability,inhibition,plugging loss reduction and bentonite addition of PEM system are optimized and evaluated.The optimized PEM system has a temperature resistance of 180℃,good rheological properties and low water loss,the rolling recovery rate of 92.5%at 150℃,and the lubrication coefficient of 0.087~0.11,which has achieved good results in application.Using logging data,the depth of drilling fluid invading into the reservoir is less than 30 cm,and the reservoir protection effect is good.The drilling fluid system has achieved good application results in many oil and gas fields with poor porosity and permeability conditions and complicated geological conditions in the Xihu sag of the East China Sea.