洛带气田蓬莱镇组层序格架下的沉积相研究

Sedimentary Facies in a Sequence Stratigraphic Framework of Penglaizhen Formation,Luodai Gasfield

四川盆地西部洛带气田蓬莱镇组为浅水三角洲—湖泊相沉积,其储层发育的主要沉积微相为三角洲前缘水下分流河道和河口砂坝。利用录井、测井资料,依据层序地层学理论,将蓬莱镇组划分为2个长期和5个中期层序旋回,并推断出沉积期湖平面的变化及其对沉积环境的影响,由下到上总体表现为水体逐渐变浅、能量逐渐增大、由加积到进积的演变过程。在层序地层格架下,对蓬莱镇组主力产气砂层的沉积微相平面展布特征进行了分析,认为研究区在以三角洲前缘亚相为主的沉积环境中,主要发育两条北东—南西向展布的水下分流河道,各个时期河道侧向迁移不大。同时指出研究区蓬莱镇组气藏天然气的产出与沉积微相之间存在着密切关系。

Penglaizhen Formation in Luodai gasfield,westernS ichuan Basin,is of a deposition of both shallow delta and lacustrine facies.And the mainly developed sedimentary microfaciesa re underwater distributary channel and channel mouth bar of delta front.In this study,based on mud-logging and well-logging data as well as sequence stratigraphy,Penglaizhen Formation can bed ivided into 2 long-term and 5 middle-term sequence cycles atf irst;and then,lacustrine level change during sedimentary perioda nd its effect on sedimentary environment are also presented,ing enerally occurring upward an evolution procedure which waterbody becomes gradually shallower and energy becomes graduallyl arger and from aggradation to progradation;thirdly,the planar distribution of sedimentary microfacies in the mainly gas-produceds ands is analyzed,and it is considered that two underwater distributary channels of both NE-ward and SE-ward are dominantly developed in a sedimentary environment with the delta front subfacies as the soul,and there is a little lateral migration during everyp eriod.At last,it is pointed out that there is a close relationship between gas production and sedimentary microfacies of PenglaizhenF ormation gas reservoir.