油基钻井液条件下西湖凹陷低孔低渗储层流体性质随钻快速识别方法

为了解决西湖凹陷低孔低渗储层流体性质快速识别困难的问题，提出了基于油基钻井液条件的时移电阻率测井对比识别法。首先进行了油基钻井液滤失性试验，研究了其在低孔低渗储层的滤失特征；然后分析了油基钻井液条件下随钻电阻率测井时、钻井液滤液侵入不同深度和侵入不同类型地层后的地层电阻率变化特征。研究表明，油基钻井液存在一定的滤失，其滤失量和岩石物性、压差和时间都有一定关系；油基钻井液滤液不导电，其侵入储层后，如果驱替的是油气，随钻和复测电阻率基本一致；如果驱替的是地层水，则复测电阻率会大于随钻电阻率。因此，利用油基钻井液的高侵特性，基于时移测井理念，提出通过对比浅层实时电阻率与复测电阻率的差异快速识别流体性质的方法。该方法进行了现场应用，流体性质快速识别结果与后续电缆地层测试泵抽取样结果一致，验证了其可行性，具有推广应用价值。 

A Fluid Properties while Drilling Rapid Identification Method under Oil-Based Drilling Fluid Conditions for Low Porosity and Low Permeability Reservoirs in the Xihu Sag

In order to achieve rapid identification while drilling of fluid properties for low porosity and low permeability reservoirs in the Xihu Sag under oil-based drilling fluid conditions, a delay-resistivity logging comparison identification method was proposed. The fluid loss test of oil-based drilling fluid was carried out, and its fluid loss characteristics in the low porosity and low permeability reservoirs were studied. The characteristics of resistivity change after the drilling fluid filtrate intruded into the different depths and types of formations during the resistivity LWD under oil-based drilling fluid conditions were analyzed. The study found that there was a certain fluid loss in the oil-based drilling fluid, and the amount of fluid loss showed a certain relationship with in-situ physical properties, along with pressure difference and time. The oil-based drilling fluid filtrate was not conductive, and if it invaded the reservoir, and the oil and gas were displaced, the resistivity of LWD and re-tested one were basically the same. If the formation water was displaced, the re-tested resistivity increased, and it could be greater than the resistivity of LWD. Therefore, based on the high intrusion characteristics of oil-based drilling fluids, according to the time-lapse logging concept, a method was proposed to that could quickly identify the fluid properties by comparing the difference between the shallow real-time resistivity and the re-tested resistivity. This method was successfully applied in the field, and the obtained fluid properties rapid identification results were consistent with the results of subsequent cable formation test pumping, indicating that this new technique was feasible and in addition, could potentially have widespread applications.