南美典型前陆盆地斜坡带油气成藏特征与勘探方向选择——以厄瓜多尔Oriente盆地M区块为例

Hydrocarbon Accumulation Feature and Exploration Direction Selection: Taking M Block of Oriente Basin,Ecuador as an Example

M区块是Oriente盆地重要的产油区块,但区块下一步勘探方向不明,亟需开展油气成藏特征研究。综合利用40余口井的钻井、测井和试油等资料,从系统的油藏解剖入手,总结了区块油气分布规律和成藏特征,建立了油气沿"构造脊"运移—"阶梯式"成藏模式,指明区块下一步勘探方向。研究认为M区块具有明显的油气差异聚集成藏特征:①区块具有明显的构造和断层控藏作用,油藏均位于近断层的第一构造带上,油藏类型主要为构造油藏;②圈闭充满度平面分布具有明显的规律性,由北向南依次降低:北部圈闭充满度高(充满度为1),南部圈闭充满度中等(充满度为0.59),最南部圈闭充满度为0(未充注);③油藏油水界面具有由北向南逐步抬升的特征;④油藏原油API值具有由北向南逐步变小的趋势。依据油气成藏模式认为区块北部位于油气运移来源方向,成藏条件有利,是下一步勘探方向。

M block is a major hydrocarbon production area in Oriente Basin of Ecuador, while future exploration direction and targets of the block are unclear. Studies on hydrocarbon accumulation of the block should be carried out immediately. Based on the comprehensive drilling data, logging data and well test, the paper systematically analyzes 17 reservoirs of M block and proposes the hydrocarbon distribution regulation and accumulation features, and figures out the future exploration area. The research shows that： （1）Structural background and fault have obvious controlling function on hydrocarbon distribution. Oil reservoirs all locate on the first structural belt near M fault and are mainly structural ones; （2）Trap fullness degree（FD） has obvious regulation in plane which decreases from north to south. The FD in northern part such as M4A _01,M4A_02,M4A_03,M4A_09,M_21,M_01 are as high as 1,while the FD of M15 in southern area is in- termediate of 0.59 ,and the FD of M16 in the south edge is 0 which means no charging; （3）The OWC of the reservoirs step up from north to south; （4）Crude oil API degree decreases from north to south. All these accumulation features match the differential entrapment theory, based on which, a hydrocarbon accumula- tion model is established where hydrocarbon migrates along the structural belt and accumulates in a multi- step way, i. e. , hydrocarbon sourced from the northern kitchen, migrated along the structural ridge and was entrapped in multistep traps. The northern part of M block,locates on the hydrocarbon migration path and close to source kitchen, has good accumulation condition and is the favorable area for future exploration.