渝东北地区WX2井页岩气赋存特征及其勘探指示意义  

Shale Gas Occurrence Characteristics and Exploration Significance of WX2 Well in the Northeast Chongqing

作　　者：付常青[1,2] 朱炎铭[1,2] 陈尚斌[1,2] 梁峰[2,3] 

机构地区：[1]中国矿业大学煤层气资源与成藏过程教育部重点实验室,徐州221116 [2]中国矿业大学资源与地球科学学院,徐州221008 [3]中国石油勘探开发研究院廊坊分院,廊坊065007

出　　处：《高校地质学报》2016年第4期679-689,共11页Geological Journal of China Universities

基　　金：煤层气资源与成藏过程教育部重点实验室(中国矿业大学)开放基金资助项目(2016-005);国家自然科学基金项目(41272155);国家基础研究发展计划(973)项目(2012CB214702)联合资助

摘　　要：为了深入研究渝东北地区龙马溪组页岩气赋存特征,该文以WX2井页岩高温高压等温吸附及覆压孔隙度实验数据为基础,通过误差最小原则挑选了适合研究区的吸附模型,并基于孔隙度随有效应力变化关系建立游离气模型,综合分析了吸附气、游离气及总含气随埋藏深度的变化特征。研究结果表明:WX2井页岩不同温度下过剩吸附量随着压力增大,均呈现先增大后减小的趋势,随着温度的升高,最大吸附量逐渐减小,而校正后的绝对吸附量随压力增加,先迅速增大后增速放缓,且用D-A模型拟合绝对吸附量数据平均误差最小,基本可以反应研究区页岩真实吸附过程。页岩样品在加压过程中孔隙及微裂隙会逐渐闭合,卸压时绝大部分会重新打开,存在部分塑性变形造成的不可逆损伤,但不可逆损伤所占比重较轻。不同方向样品孔隙度与有效应力之间具有负指数关系,富含层理页岩平行样品较垂直样品具有更大的初始孔隙度以及更强的孔隙应力敏感性。页岩气赋存特征综合受控于储集层特征、吸附能力、温度及压力等因素,其中温度对吸附气和游离气含量为负效应,储层压力为正效应;吸附气、游离气及总含气量均遵循先增大后减小的总体趋势,其中吸附气及游离气含量分别主要受控于温度及储层压力。此外,临界深度上下,页岩吸附态与游离态相对含量发生变化,其对页岩气富集评价具有重要意义。To study the shale gas occurrence characteristics of the Longmaxi Formation in northeast Chongqing, the isothermaladsorption data under high temperature and high pressure and porosity data under burden pressure of the well WX2 shale wereanalyzed. According to the principle of minimum error, we have chosen a suitable adsorption model for the study area. Based on therelationship between porosity and effective stress, the free gas model is established. In addition, comprehensive analysis of thecharacteristics of adsorption gas, free gas, and changes in total gas with the buried depth was conducted. The results show that excessadsorption quantity of well WX2 shale increased first and then decreased under different temperatures with an increasing pressure. Themaximum adsorption capacity decreased gradually as the temperature increased. After correction, the absolute adsorption quantity shows a rapid increase first and then a slow increase with increasing pressures. As the absolute adsorption data can be fitted with D-A model with the minimum average error, it can represent the real adsorption process of shale in the study area. Pores and micro-cracks of shale samples will gradually close during pressurization, and reopen during depressurization. This process will cause irreversible damage by plastic deformation, but irreversible damage accounts for small proportion. Porosities of samples from different directions have a negative exponent relationship with effective stress. Parallel samples of lamina-rich shales have greater initial porosity and stronger pore stress sensitivity than the vertical samples. Shale gas occurrence characteristic is comprehensively controlled by reservoir characteristics, adsorption capacity, reservoir temperature, and reservoir pressure. Among them, temperature has the negative effects on adsorption gas content and free gas content, and the reservoir pressure has the positive effect. The adsorption gas content, free gas content and total content increases first then decreases. Adsorption gas

关 键 词：WX2井 赋存特征 含气量 临界深度 渝东北 

分 类 号：P618.1[天文地球—矿床学]