基于地层测试数据,利用声波时差的等效深度法以及数值模拟方法对辽中北洼地区超压的分布和演化进行了研究。结果表明本区超压普遍发育,储层超压主要发育于古近系及潜山,最大压力系数1.93;东二下亚段及以下地层泥岩段中普遍发育欠压实,计算压力系数可达到1.9以上。不均衡压实和生烃作用是泥岩层超压发育的主要成因,它源传导型是储层超压发育的主要机制。沙河街组沉积以来,烃源岩中超压开始发育并逐渐增加,东营组沉积末期达到高峰,随后开始泄放降低,明下段沉积期开始,超压再次积累增大直至现今。JZ20-2凝析气田的储层流体包裹体及温压方面的证据、油气成熟度和烃源岩生烃史方面的证据以及原油物性方面的证据表明其油气成藏为晚期幕式快速充注成藏。同时研究区断裂发育少,活动性弱,油气沿断层垂向运移受限,充注期主力烃源岩发育强超压,产生水力破裂微裂缝成为油气幕式排放的通道,同时为油气长距离的侧向运移提供了充足的动力,属于超压主导型油气晚期幕式快速成藏。
Based on the data of DST and FMT, the distribution and evolution characteristics of overpressure in Northern Liaozhong subdepression are analyzed by applying interval transit time and numerical simulation method. It is suggested that overpressure is extensively developed in the basin. The reservoir overpressure which the max pressure coefficient is 1.93, is mainly developed in Paleogene formation and buried hill formation. The undercompaction is extensively developed in Lower Dongerxia Formation and the calculated pressure coefficient can reach 1.9 and more. Compaction disequilibrium resulted of high sedimentary rate and hydrocarbon generation are main factors for the development and evolution of overpressure in shale intervals, while the main mechanism of reservoir overpressure is the migration and charging of the overpressure fluids from source rock in the centre of subdepression. Overpressure developed since the Shahejie Formation deposits and increased gradually until the end of Dongying Stage, then decreased. From Mingxia Formation deposits, overpressure increased once more and reached the maximum now. This paper studied the characteristics of fluid inclusions and geothermal with pressure in reservoirs, the history of hydrocarbon generation and maturity of oil and gas, the physical properties of petroleum. It is suggested that the process of petroleum accumulation is episodic and late rapid. The migration of petroleum along the faults is limited as the development and activities of faults is weak. Hydraulic fracture caused by overpressure developed in source rock is the major conduit for episodic hydrocarbon expulsion; meanwhile, overpressure is a favorable power for long lateral hydrocarbon migration. It is suggested that overpressure-dominated controlled episodic and late rapid petroleum accumulation.