Characteristics of Fault Cementation Zone and Its Origin in Linpan Oil Pool of the Huimin Depression
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摘要: 惠民凹陷临盘油区断块油田广泛发育, 但对其封闭机制认识不清.从临盘复杂断块油田的实际地质资料出发, 依据岩心、测井资料, 结合物性、扫描电镜等实验分析, 探讨了断裂胶结带的基本特征和形成机制.研究表明, 临盘油区富含钙镁离子的地层水在断裂活动过程中沿断裂向上流动, 随着压力的降低导致在断层附近砂岩中易形成方解石、白云石等矿物的沉淀, 从而形成了致密的断裂胶结带, 胶结带内孔渗性急剧变差, 喉道半径和渗透率约降低一个数量级, 成为封堵油气的有利屏障.Abstract: Fault block oil reservoirs are well developed in Linpan oil pool of the Huimin depression. But the sealing mechanism of fault is not clear. The fault cementation zone characteristics and its origin are discussed by means of core data, well logging data, physical property and scanning electronic microscope analysis. The subsurface water rich in Ca2+ and Mg2+ migrates from deep formation to shallow part along the fault zone during faulting activity in Linpan oil pool. Calcite and dolomite deposit along the fault zone due to the decreasing geothermal pressure upward. As a result, the permeability of the fault zone decreases about one order of magnitude and the accumulated oil is well sealed by fault cementation zone.
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表 1 断裂胶结带砂岩与正常砂岩成分对比
Table 1. Correlation of sands in fault cementation zone and normal sands
类别 正常砂岩 断裂胶结带 陆源碎屑(%) 石英 45.0 46.4 长石 33.3 34.3 岩屑类 21.5 19.2 填隙物(%) 泥质 6.1 0.8 方解石、白云石等矿物 5.2 25.3 合计 11.3 26.1 孔隙体积(%) 孔隙度 14.3 4.8 表 2 临南洼陷各层位油田水
Table 2. Field water of different strata in Linnan sag
层位 矿化度(mg/L) CO32- SO42- Cl- Ca2+ K++Na+ Mg2+ Na+/Cl- 水型 样品数 Ng 9031 318 40 5955 214 3276 68 0.56~0.92 CaCl2 36 Ed 18495 484 64 10171 227 6373 94 0.55~0.97 CaCl2 42 Es1 25224 618 43 14334 567 8659 172 0.41~1.29 CaCl2 65 Es2 29122 664 165 16534 849 9783 312 0.21~1.57 CaCl2 181 Es3 38573 630 119 22082 1574 12385 308 0.36~1.33 CaCl2 78 Es4s 57475 345 349 35799 3229 17881 528 0.45~0.97 CaCl2 43 Es4x 102933 264 610 68757 16351 41790 42084 0.45 CaCl2 8 表 3 温度对碳酸盐岩淋溶作用的影响
Table 3. Leaching effect of temperature on carbonate
温度(℃) 溶解时间(h) 1g样品淋溶数量(mg/h) MgCO3 CaCO3 CaMg(CO3)2 25 5.75 0.20 0.42 0.62 50 4.5 0.22 0.69 0.91 -
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