东海某气井低渗储层特征评价及污染因素分析

东海深部地层低渗透油气资源储量巨大，受制于储层本身物性和钻完井施工影响，部分气井储层保护效果不理想。以东海某气井低渗储层岩心资料为基础，开展润湿性、非线性渗流、核磁共振、钻井液损害储层室内评价实验，揭示了低渗储层基本特征及渗流规律，评价了该类储层的可动用性。结合钻完井施工情况，进一步分析了导致该气井低渗储层污染的影响因素。研究表明，该气井低渗储层岩石亲水，孔喉细小，发生水锁后不易解除。低压力梯度下存在明显的非线性渗流特征。10 ×10?3 μm2以下储层可动流体百分数低于57.86%，属于三类储层，动用难度大。相比浸泡时间，钻井压差损害更大，压差应尽可能控制在3.5 MPa以内。

Low Permeability Reservoir Characteristics Evaluation and Pollution Factor Analysis of A Gas Well in East China Sea

There are huge reserves of low permeability oil and gas resources in the deep strata of East China Sea. Restricted by the physical properties of the reservoir itself and the impact of well drilling and completion, the protection effect of some gas wells is not ideal. Based on the low permeability reservoir core data of a gas well in East China Sea, the laboratory evolution experiments of wettability, nonlinear seepage, nuclear magnetic resonance and drilling fluid damage are carried out, and the basic characteristics and seepage law of low permeability reservoirs are revealed, and the availability of such reservoirs is evaluated. Combined with the drilling and completion of the well, the influencing factors of the low permeability reservoir pollution of the gas well are further analyzed. The study shows that the low permeability reservoir rock of this gas well is hydrophilic and the pore throat is small, so it is not easy to release the water lock after it occurs. The characteristics of nonlinear seepage are obvious under low pressure gradient. The percentage of movable fluid in the reservoir below 10×10?3 μm2 is less than 57.86%, which belongs to the third class of reservoirs, and is hard to mobilize. Compared with the soaking time, the damage of drilling pressure differential is greater. Thus the drilling pressure difference should be controlled within 3.5 MPa as far as possible.