山前构造砾石层气体钻井井壁稳定评价新方法

塔里木油田山前构造带砾石层气体钻井提速效果明显,但砾石层井壁垮塌问题突出,开展砾石层井壁稳定性评价,筛选气体钻井适宜井段是该地区提速增效的关键。通过测试山前构造带巨厚砾石层地面露头岩样粒间填隙物矿物组分含量、微观结构、水理化性能、声波速度特性及力学参数变化规律,再结合现场工程测井资料等信息,对比了西域组、库车组、康村组及吉迪克组砾石层测井响应特征及其与气体钻井井壁稳定性之间的关系。建立了一套砾石层气体钻井井壁稳定评价新方法。评价结果认为,西域组和库车组砾石颗粒间黏土含量高,遇水易分散,气体钻井井壁易垮塌,不适宜气体钻井;康村组和吉迪克组砾石颗粒间以方解石、白云岩为主,胶结强度高,井壁稳定性好,适宜气体钻井。

A new method for evaluating the stability of gas drilling wellbore for gravel layer

The drilling rate increase prominently by gas drilling in gravel layer of piedmont tectonic belt in Tarim oilfield, but the problem of wellbore collapse in gravel layer is outstanding. The key point of increase drilling rate and efficiency is carrying out the evaluation of wellbore stability in the gravel layer and screening the appropriate section for gas drilling. This study was systematically tested the mineral component content, microstructure spatial distribution, hydro physical and chemical properties, acoustic velocity characteristic and the law of mechanical parameters variation of the outcrop coming from gravel layer of piedmont tectonic belt. Combining with the actual logging date, we studied the log response characteristics of gravel layer in Xiyu group, Kuche group, Kangcun group and Gidike group formations and its connection with wellbore stability. Comprehensive analysis of various data, established a new method for stability evaluation of gas well wall in gravel layer. The results show that the clay content between the gravel particles of the Xiyu group and the Kuche group is high, and it is easy to disperse when exposed to water. The gas drilling well wall is easy to collapse in the Xiyu group and the Kuche group, and it is not easy to use gas drilling; The cement between the Kangcun group and the Gideke group is mainly composed of calcite and dolomite, with high cementation strength and good stability of the borehole wall, which is suitable for gas drilling.