澳大利亚Bonaparte盆地WA-406-P区块油气成藏条件及控制因素

Bonaparte盆地属于陆内裂谷与被动大陆边缘相叠加的叠合型盆地，WA-406-P区块就位于盆地早-中侏罗世发育的大型Plover三角洲沉积体系之上，该区块油气成藏条件及控制因素的研究是确定下步有利勘探目标的前提与基础。本文结合油气地质、分析化验、三维地震、测井曲线等资料进行综合分析，研究表明：WA-406-P区块发育两种烃源岩类型，西北部以Ⅱ₁型为主，东南部以Ⅱ₂型为主，成岩作用控制着储层的储集性能，整体上属于低孔高渗透型储层；中-下侏罗统的Plover组和Elang组及上侏罗统-下白垩统的Flamingo组三套三角洲砂体与大套的海相泥岩配置形成两套有利储盖组合，由于圈闭形成期早于大规模油气运聚期，因此，油气经历两期充注后，具备良好的成藏匹配关系。烃源岩分布特征控制着油气藏的流体类型，构造形态及断层展布控制着油气藏的类型，储层物性控制着油气地质储量的丰度，断层活化作用控制着油气藏能否完整保存。油气成藏控制作用的明确指明了有利勘探区域：北部垒堑间互带为Ⅰ类勘探区，西南斜坡带为Ⅱ类勘探区，东南洼槽区为Ⅲ类勘探区。

Hydrocarbon Accumulation Condition and Controlling Factors of Block WA-406-P in Bonaparte Basin,Australia

The Bonaparte basin is a superimposed basin where the intra-continental rift and passive continental margin are superimposed, and the block WA-406-P is located in the large Plover delta sedimentary system formed in Early-Middle Jurassic in this basin. In this study, the comprehensive analyses were conducted on oil & gas geology, experimental data, 3D seismic, well logging curves and so on, to find out the hydrocarbon accumulation conditions and controlling factors, and then to specify the next exploration target area. The research results show that in the block WA-406-P, two types of source rocks are developed:one is type Ⅱ₁ in the northwestern region and the other one is type Ⅱ₂ in the southeastern region. The reservoir is controlled by diagenesis for its capacity, and belongs to low porosity and high permeability reservoirs. Three sets of delta sand bodies in the Plover and Elang Groups of Middle-Lower Jurassic and the Flamingo Group of Upper Jurassic-Lower Cretaceous combined with large set of marine mudstones formed two sets of favorable reservoir and cover combinations. Because the traps formed earlier than the large-scale oil & gas migration and accumulation, the block WA-406-P had very good conditions for hydrocarbon accumulation when the reservoirs were filled within the two different periods. With the analysis of hydrocarbon accumulation conditions, the controlling factors of hydrocarbon accumulation were also determined. The main results indicate that the distribution characteristics of source rock control the fluid type of oil & gas reservoir, the structural morphology and fault distribution control oil & gas reservoir type, the reservoir properties control the abundance of geological reserves, and the fault activation effect controls whether oil & gas reservoir can be preserved. On the above analysis, the favorable exploration areas are determined as below:the first class is in the inter zone of horst and graben in the northern block, the second class is in the slope zone in the southwestern block, and the third class is in the trough zone in the southeastern block.