大宁-吉县河西区块深部煤层破裂压力预测及分布特征

Prediction and distribution characteristics of deep coal seam fracture pressure in Hexi Block of Daning-Jixian

深部煤层破裂压力的精准预测及分布特征直接关系到井壁稳定性评价与储层可压性评价。为进一步建立深部煤层破裂压力计算模型和明确破裂压力空间分布特征,以大宁-吉县河西区块深部8^(#)煤层为研究对象,在充分挖掘地球物理测井信息的基础上,引入抗拉强度、煤体结构指数、裂缝发育程度等因素,给出了深部煤层破裂压力理论模型,并明确了垂向应力、孔隙压力、抗拉强度、有效应力系数、泊松比、弹性模量等参数的测井求取方法,进而形成了适用于深部煤层的破裂压力计算模型。通过将该套方法程序化,实现了区块内深部8^(#)煤层的破裂压力计算机可视化自动处理,并建立了8^(#)煤层破裂压力三维空间地质模型。结果表明:基于测井资料建立的深部煤层破裂压力计算模型能够对区块内深部煤层破裂压力进行精准预测,最大相对误差为13.2%;破裂压力低值区主要分布在中部—东北部、西南—中南部井区。该方法可为地球物理测井预测深部煤层破裂压力提供一种新途径,为井壁稳定性评价和储层可压性评价提供技术支撑。

The accurate prediction and distribution characteristics of deep coal seam fracture pressure are directly related to the evaluation of borehole stability and reservoir fracability.In order to further establish a calculation model for deep coal seam fracture pressure and clarify the spatial distribution characteristics of fracture pressure,the deep 8^(#)coal seam of Hexi Block in Daning-Jixian was taken as the research object.On the basis of fully excavating geophysical logging information,the theoretical model of the fracture pressure of deep coal seam is given by introducing factors such as tensile strength,coal structure index and fracture development degree.The logging methods of vertical stress,pore pressure,tensile strength,effective stress coefficient,Poisson′s ratio,Young′s modulus and other parameters are defined,and then a calculation model of fracture pressure suitable for deep coal seam is formed.By programming the method,the computer visualization and automatic processing of the fracture pressure of the deep 8^(#)coal seam in the block are realized,and the three-dimentional spatial geological model of the fracture pressure of the 8^(#)coal seam is established.The results show that the deep coal seam fracture pressure calculation model based on logging data can accurately predict the deep coal seam in the block,and the maximum relative error is 13.2%.The low value area of fracture pressure is mainly distributed in the middle-northeast and south-southwest well areas.This method can provide a new way for geophysical logging to predict the fracture pressure of deep coal seam,and provide technical support for wellbore stability evaluation and reservoir fracability evaluation.