加强岩石物理研究 提高油气勘探效益

Strengthening Petrophysical study to raise exploration benefit

随着我国油气勘探以低幅度构造、低孔、低渗储集层和裂缝性复杂岩性储集层为主要目标，从而使测井技术大量面对低电阻油层和复杂油气藏以及不利测井环境。介绍了近１０年来油气层测井评价方面的岩石物理研究成果：①渤海湾地区低电阻油层形成机理有：滩海地区海水钻井液在低幅度油气藏背景下深侵入，使油层视电阻率成倍下降；油层具有复杂的双组孔隙系统，平均含水饱和度高使电阻率变低；油层的黏土矿物附加导电现象造成低电阻。②低孔、低渗油层试油获得率不高的原因主要有：钻井液侵入低幅度构造油藏油水过渡带造成高侵剖面，侧向测井电阻率比实际偏高许多；孔隙度小于１２％的储集层孔隙结构对电阻率影响很大，必须区分孔隙结构，才能用电法测井来评价油层或干层。③裂缝性储集层的基质与被钻井液侵入的裂缝的电性相差极大，双侧向测井对高角度裂缝发育的砂岩油层可进行识别和定量评价，可以用双侧向及中子、密度测并对裂缝性储集层进行分类评价。简述了适用于低电阻油层和低孔、低渗油层以及裂缝性储集层的电法测井技术。今后要研究钻井液侵人与孔隙结构对油层电性质和电法测井响应规律的影响，采用“及时测井”和压力梯度测井等技术措施；测井计算饱和度技术已日趋成熟，但需采用高精度数控测井等?

In recent years, the China's oil and gas exploration focuses on low-relief structure, low-porosity, low-permeability and complex lithology reservoirs. The log technology has to face low-resistivity and complicated reservoirs and some other disadvantageous conditions. This article introduces some petrophysical study achievements of oil/gas-bearing formation log interpretation in recent 10 years: (1) The formation of low-resistivity pay zones in Bobai Bay is due to the fact that sea-water drilling mud invaded into oil/gas-bearing formation; Complex dual pore texture of pay zones with high average water saturation and additional conductivity of the clay minerals. (2)The reasons of low testing successful ratio of low-porosity, low-permeable pay zones are drilling-mud invaded into oil-water transitional zone of low-relief structure reservoir, leading to high invaded section and so laterolog resistivity being much high. For porosity bigger than 12%, influence of the pore texture on the resistivity is much big. So using electric log to interprete pay zone or not must be based on the pore texture partition. (3 )The resistivity of matrix is quite different from that of the drilling-mud-invaded fracture, and dual laterolog can recognize and quantitatively evaluate the high angle fractured sandstone oil zones. Dual laterolog log, neutron and density log can interprete fractured reservoirs. This article summarizes the electric log technology applying to low-resistivity, low-porosity, low-permeable pay zones and fractured reservoirs. To study the influence of drilling-mud invasion and pore texture to oil zone resistivity and its electric log response rule, 'in-time log' and pressure gradient log should beapplied. Though the logging-based saturation interpretation technology becomes mature, the high precision numerical control log, more subtle' core calibration log' interpretation method are needed to meet much more demands. Finally the author gives some suggestions on making feasible petrophysical technology policies.