东营凹陷深层裂解气成藏主控因素

东营凹陷深层裂解气藏为凝析气藏和纯气藏,气源来源于沙四下亚段高成熟烃源岩。通过分析化验、测井、地震等资料综合研究了裂解气成藏控制因素。研究表明,地温直接控制油气生成、烃类相态和气藏分布;近岸水下扇相扇中辫状水道和前缘微相储集层物性较好,是裂解气成藏的主要储集层,溶蚀作用改善了储集层条件,提高了含气性;流体势控制了油气运移和聚集成藏,由凹陷中心的高势区向边部低势区运移,在断裂陡坡带有利相带的砂砾岩体中聚集形成裂解气藏。东营凹陷北部断裂陡坡带是深层裂解气富集和分布的区带,也是近期深层天然气勘探的方向。

The Main Controlling Factors of Deep Cracked Gas Accumulation in Dongying Sag

The deep cracked gas pool in Dongying sag is charaeterized by condensate gas reservoir and net gas reservoir. The gas snarce originates from high matured source rock of the lower sub-section of Es4. The factors controlling the eracked gas accumulation are studied by lab experiment, well log and seismic data analyses. Study shnws that the hydrnearbon generation, hydrocarbon phase state and gas reservoir distribution are all controlled by in-situ geotemperature; the main reservoirs for the cracked gas accumulation are the mid-fan braided channel microfacies and front mierofaeies in nearshore submerged fan facies, and the reservoirs conditions are improved by solution proeess, hence rising the gas-bearing property in them, the hydrocarbon migration and accumulation are controlled by the fluid potentials, allowing hydrocarbons to migrate from high potential zone in sag center to low potential zone at verges. finally to accumulate, in the glutenites of favorable facies zones in faulted abrupt slope belt. It is concluded thai the faulted abrupt slope belt in northem Dongying sag is an area for the deep cracked gas enriehment and distribution, thus it is also as a target for deep natural gas prospecting in the near future.