钻井液侵入时水合物近井壁地层物性响应特征  

Physical Properties Response of Hydrate Bearing Sediments near Wellbore during Drilling Fluid Invasion

作　　者：郑明明[1,2,3] 蒋国盛[3] 刘天乐[3] 彭力[3] 宁伏龙[3] 刘力[3] 陈中轩[4] 王震[3] 

机构地区：[1]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083 [2]中南大学地球科学与信息物理学院,湖南长沙410083 [3]中国地质大学工程学院,湖北武汉430074 [4]国家海洋局第二海洋研究所,浙江杭州310012

出　　处：《地球科学（中国地质大学学报）》2017年第3期453-461,共9页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(Nos.40974071;51274177;41502346);湖北省自然科学基金重点项目(No.2012FFA047);中国地质大学(武汉)中央高校基金项目(Nos.CUGL100410;CUG120112;G1323511453);中国地质大学(武汉)实验技术项目(No.CUGL140819);中南大学有色金属成矿预测与地质环境监测教育部重点实验室开放基金资助项目(Nos.2016YSJS005;2016YSJS011)

摘　　要：目前,国内外学者对钻井液侵入水合物地层的室内实验模拟研究停留在较小尺度上且可靠性难以验证,尚需利用与实际地层物性参数较为贴近的沉积物模型,开展大尺度的实验模拟,为改善水合物地层钻井过程中钻井液工艺和测井准确识别与评价水合物储层提供依据.根据墨西哥湾水合物地层主要物性参数指标压制了相应的人造岩心,进行了人造岩心钻井液侵入实验.结果表明:水合物在加热分解过程中,温度与压力呈上升趋势,而电阻率先升高后下降,水合物相平衡条件不仅与温压条件有关,还受孔隙水盐度不断变化的影响。钻井液侵入岩心过程中,压力的传递速率快于热量的传递,易使原始岩心孔隙中的水、气在压力升高而温度尚未改变的情况下生成二次水合物.钻井液温度是水合物分解的主要因素,而压差有利于提高孔隙水压力,保持水合物的稳定.高密度钻井液虽有利于形成高压差和抑制水合物在钻井液中形成,但也会导致钻井液低侵并使井周水合物更易分解.因此,在实际水合物地层钻井中,为了减少钻井安全事故,应在安全密度窗口范围内尽可能提高钻井液密度,选用温度较低的钻井液并加入一定量的动力学抑制剂或防漏失剂.电阻率测井应该选用随钻测井方式或者深侧向测井值,从而避免因水合物分解导致的测井失真.At present, the laboratory experiment of drilling fluid invasion problem mostly locus on smaLL-sere J＊.-e --- large-scale experiment based on physical parameters more similar with actual sediment would provide guidance for drilling fluid formulation during actual drilling process in hydrate-bearing formation and accurate well logging identification and hydrate res- ervoir evaluation. This experiment were based on artificial cores which were made according to the physical properties of hy- drate-bearing formation in the Gulf of Mexico. Results indicate that the temperature and pressure rise when hydrate is heated to decompose, while the resistivity firstly increases and then decreasse, in which, hydrate equilibrium conditions are not only affected by temperature and pressure, but also by pore-water salinity. During drilling fluid invasion, the pressure spread rate is much faster than heat, hence it is probably that in-situ pore water and gas continue to form hydrate for pressure increase while temperature doesn＇t change. The high drilling fluid temperature is the main factor controlling hydrate decomposition, and pres sure difference between drilling fluid and pore pressure can help improve the pore water pressure, which is beneficial to hydrate stability. Though high salinity drilling fluids are conducive to higher pressure difference and will inhibit hydrate formation in drilling fluid, it can also lead to gas hydrate dissociation. Therefore, in order to reduce the drilling risks in the hydrate-bearing formation, the density of drilling fluids should be increased during the safe density window range, but the density increase also increases the drilling fluid invasion. Therefore, a certain amount of kinetic inhibitors and fluid loss control agent leak loss con- trol agents should be added in the low temperature drilling fluids. At the same time, the logging while drilling method or deep laterolog data should be chosen so as to avoid the distortion caused by drilling fluid invasion and hydrate decomposition.

关 键 词：天然气水合物 实验模拟 近井壁地层 侵入 钻井安全 电阻率 工程地质. 

分 类 号：P56[天文地球—构造地质学]