顺南区块裂缝性储层置换式气侵影响因素研究

塔河油田顺南区块塔中北坡奥陶系鹰山组上段属于碳酸盐岩裂缝孔洞型储层，钻进该层段时气侵现象严重，现场常采用提高钻井液密度和循环排气的方式处理气侵。为解决裂缝性储层在高密度钻井液条件下易发生漏失、循环排气方式处理时间较长等问题，对裂缝性储层置换式气侵发生时间的影响因素进行了研究。通过建立漏失速率模型与置换式气侵模型，分析了裂缝宽度、高度、长度，地层压力、压差及钻井液的黏度、密度对气侵发生时间的影响。研究发现，裂缝宽度越小、高度和长度越大，钻井液黏度越大、密度越小，以及地层压力越低、压差越大时，气侵发生时间越长。研究结果表明，现场施工中合理控制钻井液密度和压差，可以控制和减小置换式气侵速度。 

A Study on the Effect of Displacement Gas Cut on Fractured Reservoirs in Shunnan Block

The upper section of Ordovician Yingshan Formation on Tazhong Northern Slope of Shunnan Block in the Tahe Oilfield belongs to a type of porous fractured carbonate reservoir.in this type reservoir,gas cut is the most serious during drilling,and this gas cut is often treated by increasing the density of drilling fluid and circulating the drilling fluid to exhaust the gas in the field.In order to solve the problems of high density drilling fluid,including its tendency to leak,and long treatment time required for exhaust circulation,researchers studied the factors that most influenced the gas cut time of gas-liquid displacement in the fractured reservoir.The viscosity and density of the drilling fluid on time required for gas cut were analyzed by building the leaking rate model and a gas cut model. Thus it was possible to evaluate effects of width,height and length of fracture,formation pressure and pressure difference..It was found that gas cut is slower under conditions of smaller width,greater height and length of fracture,greater viscosity and smaller density of drilling fluid,as well as lower pressure and greater pressure difference of formation.Therefore,proper drilling fluid density and pressure difference control measure are necessary for field operation to effectively inhibit and reduce the displacement gas cut rate.