高温高压气层的钻井液伤害室内定量评价方法
Laboratory Quantitative Evaluation Method of Drilling Fluid Damage in High Temperature and High Pressure Gas Reservoir

高温高压条件下，钻井液性能会降低，现有的低温低压钻井液伤害室内评价方法难以适应逐渐成为勘探开发热点的深层或深海高温高压储层。在对比已有评价方法的基础上，重新设计了高温高压室内钻井液储层伤害实验流程。新提出的高温高压动态滤失实验装置可承受最高温度和压力可达到230℃和70 Mpa，并且新的钻井液伤害评价流程中增加了水基钻井液动态滤失实验、岩心束缚水状态下的渗透率对比(K2、K4)、微观伤害机理实验。新的评价方法在珠江口盆地白云凹陷深水区的高温高压气层进行了应用。结果表明，在高温高压下，动态滤失时间约为120~205 min时，岩心达到完全污染状态；钻井液对岩心的绝对伤害率为49.94%~69.77%，相对伤害率为42.44%~97.33%；对低孔渗岩心，相对伤害率大于绝对伤害率，高孔渗岩心则相反；钻井液中固相颗粒侵入岩心，附着在岩心孔隙内、堵塞喉道，从而污染岩心，导致岩心渗透率大幅度下降。
Under high temperature and high pressure conditions, the performance of drilling fluid will be reduced. The existing low temperature and low pressure drilling fluid damage evaluation method cannot adapt to the deep-seated or deep-sea high temperature and high pressure reservoir which has gradually become the hot spot of exploration and development. On the basis of comparing with the existing evaluation methods, the experimental flow of drilling fluid damage to reservoir under high temperature and high pressure conditions is redesigned. The proposed high temperature and high pressure dynamic filtration device can withstand the maximum temperature and pressure of 230？C and 70 Mpa. In the new drilling fluid damage evaluation process, dynamic filtration test of water-based drilling fluid, permeability comparison under bound water condition (K2, K4), and microscopic damage mechanism experiment were added. The proposed evaluation method is applied to the high temperature and high pressure gas reservoir in Baiyun Sag, Pearl River Mouth Basin. The results show that, under high temperature and high pressure conditions, the core plugs were completely polluted when the dynamic filtration time is about 120 min~205 min. The absolute damage rate of drilling fluid to core plugs is 49.94%~69.77%, and the relative damage rate is 42.44%~97.33%. For low porosity and permeability core plugs, the relative damage rate is greater than the absolute damage rate, while for high porosity and permeability core plugs, it is the opposite. Solid particles in drilling fluid invade core plugs, adhere to core pores and block throat, thus contaminating core plugs, resulting in a significant decrease in permeability.