川中地区侏罗系下沙溪庙组砂岩油藏成藏分析及勘探开发建议

【作者】 刘桂侠；

【导师】 罗平亚； 沈平平； 赵文智；

【作者基本信息】 西南石油学院 ， 油气田开发， 2003， 博士

【摘要】 川中油矿是我国的老油区之一,自1954年开始勘探至今已有近50年历史,截止2001年9月,已累计完钻井1378口,发现二十余个油田及含油构造,为我国石油工业的发展做出了贡献。近年来,在川中地区的莲池地区、公山庙地区的凉高山组和下沙溪庙组砂岩储层中获得了高产工业油流,公山庙地区就新增储量近5000万吨,且油层埋藏较浅,均在3000m以内。这些勘探成果展示了川中地区良好的勘探前景。 本文选择了川中东部地区为主要研究对象,应用岩心观察、烃源岩及原油地球化学、储层实验室分析、储层地球物理预测、油藏成因分析等多种手段和方法,对下沙溪庙组的碎屑岩油藏开展成藏规律、储层发育特征进行了综合研究,并提出勘探开发对策。主要认识如下: 1.通过大量区域地层对比、沉积学研究和古流向分析重建了中侏罗统下沙溪庙期的古地理演化格架。例如,将四川盆地及毗邻地区的下沙溪组（J₂x）沉积相划分为冲—湖积平原、冲—洪积平原（河—湖—沼交织相）和滨浅湖夹三角洲前缘三大相区,这较之前人笼统称之为洪泛盆地前进了一大步。并在此基础上,首次初步确定了川中地区J₂x、油藏储集砂体的古流向为自N→S和由E→W。 2.下沙溪庙组砂岩油藏的油源岩为大安寨组和凉高山组,属半深湖相沉积,源岩广布川中,有机质丰度高、类型好;沙底也发育源岩。源岩在仪陇—平昌凹陷处高成熟阶段（R_o=1.7—1.8%）;而川中油区构造低部位刚刚成熟。油/源对比结果表明,川中地区许多油藏原油的甾烷参数与当地源岩的可比性较差,原油可能主要为异地源岩所生并侧向运移而来。 3.据岩芯观察、露头剖面考察和薄片鉴定,在四川盆地覆盖区侏罗系首次发现浊沸石次生溶孔储集砂体,预示该区可能会有良好储层。另外,根据近800个物性分析数据的统计分析,下沙溪庙组砂岩储层的具超低孔、超低渗特征。 4.针对川中地区砂岩储层的地质实际,本论文应用地球物理储层预测技术,对下沙溪庙组底部河流相薄砂层、河流相厚砂体的进行预测,获得了更多还原

【Abstract】 Oil field in central Sichuan basin is one of the oldest oil field in China. Since 1954 it has been explored oil and gas for about 50 years in this area. Up to 2001, 1378 wells has been drilled, and more than 20 oil fields or structures which reserve oil have been found. Therefore oil production in central Sichuan basin contributed to Chinese petroleum industry. In the past few years, a great amount of oil has been produced from the sandstone reservoir of Lianggaoshan formation and lower Shaximiao formation in Lianchi area and Gongshanmiao area. Up to now, accumulation proven oil reserve in Gongshamiao area has been risen to 5000 ton, and almost all oil reserved in the depth less than 3000 meter. Thus central Sichuan basin is a good prospective area for oil exploration.With studying well core, source rock, geochemistry of original oil, data of analyzing reservoir samples, seismic inversion, we conclude the rule and model of forming the oil reservoir for clastic rock in Lianggaoshan and lower Shaximiao formation. And on the bases of all studied results, the significant exploration policy is provided. The major conclusion is as following.1. With much more working on regional stratigraphic correlation, sedimentology, current orientation of ancient river, paleogeograthy evolution is rebuilt from Ziliujing to upper Shaximiao in upper-middle Jurassic. For example, it is considered that in Shaximiao period the major sedimentary facies developed in the study area are fluvial plain, delta front and shallow lake, which is quite different from the previous view of flood basin. Moreover, it is the first time that we point out one of the deposit sources extend from north to south and another one is from east to west.2. In the study area, the source rock formed in semi-lake of Daanzhai and Lianggaoshan period is distributed in central Sichuan basin. Residual Organic carbon in the source rock is abundant, and the kerogen types are mainly sapropel-type or humosapropelic-type. The hydrocarbon kitchen is mainly located in Yilong-Pingchang area, where vitrinite reflectance of organic matter is about 1.7-1.8%. With comparing gonane between oil and source rock, it is concludedthat oil reserved in the central Sichuan basin does not come from local place, but come from Yilong-Pingchang area.3. With studying core, outcrop and thin sections, laumontite cement is firstly found in the Shaximiao sandstone. Moreover the secondary pore space generated by dissolving laumontite cement is the most significant porosity in the sandstone reservoir. Also, statistics data from about 800 porosity and permeability indicate that reservoir quality in lower Shaximiao sandstone is much higher than in upper Lianggaoshan formation.4. For the specific sandstone reservoir in central Sichuan basin, seismic prediction techniques have been applied in predicting sheet sandstone of lacustrine facies in Lianggaoshan formation, thin sandstone of river channel in lower Shaximiao formation, think sandstone of river channel in lower Shaximiao formation. And the prediction results are more effective.5. In central Sichuan basin, most of Jurassic oil reservoir belong to lithologic-joint and fault-lithologic reservoir. With integrated study, distribution of source rock, ancient uplift, fault or joint, and distribution of sandstone reservoir are the essential key factors to form oil pool. Moreover, the faults which connects the source rock to sandstone reservoir is the most important one.6. To sum up all petroleum geological factors in central Sichuan basin, it is considered that oil exploration is prospective, although there are many problems to deal with. It is predicted that Gongshanmiao area, Nanchong-guangan-longniushi old oil field, Shuanghechang which is located in the slope of north area of central Sichuan basin, and Tianchi area are all major targets for future oil exploration.7.Because reservoir of Shaximiao formation has character of lower porosity and permeability and potential possibility of severe formation pollution, it is suggested that we should pay more attention to reservoir pollution by drilling mud, reservoir auto-absorbing water, stress sensitivity and additive.8. Because fracture is the important oil migration path for Lower Shaximiao member, it is suggested that horizontal well technique will be used to developing oil, in order to consider reservoir pressure, sensitivity, distribution of formationstress around wells. At same time, for the specific character of the formation it is suggested that low-pressure drilling technique should be used with premium operating fluid, such as gas drilling, mist drilling, foam drilling, aerated mud drilling, under balance pressure drilling and light mud drilling.更多还原