扇三角洲砂砾岩油藏储层敏感性研究——以准噶尔盆地玛湖凹陷百口泉组为例

Fan-delta sandy conglomerate reservoir sensitivity:A case study of the Baikouquan formation in the Mahu sag,Junggar basin

以准噶尔盆地玛湖凹陷下三叠统百口泉组砂砾岩油藏为例,在从岩石学、储集空间、孔隙结构、物性方面表征砂砾岩非均质性的基础上,开展岩心流动实验,系统评价了砂砾岩储层敏感性及其影响因素.认为砂砾岩储层不同敏感性的程度有显著差异,而黏土矿物绝对总量及类型、孔隙结构主导了其储层敏感性.研究结果表明:百口泉组砂砾岩水敏指数Lw为0.31~0.66,均值0.48,水敏性中等偏弱—中等偏强;速敏损害率Dk为0.16~0.82,均值0.38,速敏性差异大,从弱至中等偏强;应力损害率Dst为0.753~0.764,均值0.76,应力敏感性强;而盐敏性和酸敏性无—中等偏弱.黏土矿物绝对总量以及伊/蒙混层、伊利石相对含量显著影响了水敏性,孔喉半径小于1.44μm的含泥砾岩水敏性较强.高岭石等分散片状黏土矿物的相对含量与孔喉大小决定了速敏性.泥质含量高,分选相对差,渗滤喉道呈片状或弯曲片状,导致砂砾岩应力敏感性显著.

Taking the Triassic Baikouquan formation（T1b）continuous sandy conglomerate reservoirs in the Mahu sag,Junggar basin as an example,and based on the comprehensive analysis of lithology,reservoir space,pore texture,physical properties characterizing the non-homogeneity of reservoir rock,core flow tests were carried out to synthetically evaluate reservoir sensitivity of sandy conglomerate as well as its control factors.It is considered that the intensity of different sensitivities in the sandy conglomerate has significant variation.Clay content,as well as clay mineral types and pore network dominate the reservoir sensitivity.The results show that,water sensitivity index（Lw）of T1 b sandy conglomerate is 0.31—0.66,with the average of 0.48,indicating that the water sensitivity is medium weak to medium strong;the flow velocity sensitivity loss ratio（Dk）is 0.16—0.82,with the average of 0.38,revealing that theflow velocity sensitivity is uneven in different rock types,which is weak to medium strong;the stress sensitivity loss ratio（Dst）is 0.753—0.764,with the average of 0.760,suggesting that the stress sensitivity is strong;the salt sensitivity and acid sensitivity are only none to medium weak.The total content of clay and relative content of illite/smectite formation and illite obviously affect the reservoir water sensitivity,so muddy conglomerate with pore throat less than1.44μm has stronger water sensitivity.The relative content of scattered patch clay minerals such as kaolinite,and pore throat size determine the flow velocity sensitivity of reservoir.High plastic clay content,relatively bad sorting,as well as plate or bending plate shaped percolation throat lead to significant reservoir stress sensitivity in T_1b.