法尔康盆地基于重力资料的构造特征分析与油气有利区预测

法尔康盆地位于委内瑞拉西北部,具有良好的油气资源前景。前人在盆地进行的勘探工作主要集中在盆地中部及东北部较小区域内,盆地整体勘探程度低且地震资料缺乏。为了研究盆地构造特征,预测油气有利区,基于地面、船测和卫星重力数据,结合盆地实际地质背景,应用莫霍面改正和倾斜角处理等方法新推断了整个盆地的断裂构造;综合应用Parker法和相关分析法计算了盆地的基底深度;利用盆地模拟软件模拟分析了不同构造单元烃源岩热演化的差异性,对盆地进行了构造单元划分及油气有利区预测。研究结果表明,法尔康盆地主要发育NE和NW向的控制盆地内构造走向和地层发育的两组断裂,盆地可以划分为6个次级构造单元,其中,西部、北部凹陷和中部隆起区地层发育较为齐全。盆地内中部隆起区及两侧的凹陷区烃源岩热演化存在差异,中部隆起区白垩系烃源岩与始新统烃源岩进入生烃门限的时间明显早于其它地区,油气地质条件良好,为油气有利区。

The Falcon Basin is located in the offshore area of northern Venezuela.It is a continental margin basin with a total area of approximately 45521km2 controlled by strike-slip faults.Although the Falcon Basin has good prospects for oil and gas exploration,limited exploration studies have been performed there,and the seismic data are deficient.Thus far,exploration works have mainly been distributed in the northwestern and northeastern of the basin in small scale.To study the overall structural characteristics of the basin and predict prospective areas of hydrocarbon,the present study adopted advanced edge recognition techniques,such as title angle (TA),to process gravity anomaly after Moho correction to obtain the fault structure information.Afterward,the present study identified and inferred the fault structure system of the study area in addition to the actual geological background of the study area and previous relevant research results.To improve the inverting accuracy of the basement depth using gravity data of the basin,the basement depth was calculated using Parkers method and correlation analysis method in addition to previous related research results.To effectively predict the favorable oil and gas areas using gravity data with scarce relevant data according to the interpretation results of gravity data and related data above,the present study uses the basin simulation software to simulate the evolution characteristic of organic matter maturity in different tectonic units of the basin,and the time at which hydrocarbon source rocks entered the hydrocarbon generation threshold was obtained.This provides a certain basis for predicting favorable hydrocarbon areas.To synthesize the fault structural system inferred and the basement depth calculated,the structural units of the basin were divided and the favorable areas of hydrocarbon were predicted.The study results were as follows:①There are mainly two groups of faults in NE and NW direction developed in the basin,and they control

the tectonic trends and cap rock development within the basin.②The Falcon basin can be divided into six structural sub-units.Among them,the strata in the western and northern depressions and the middle uplift are well developed.③The time that Cretaceous and Eocene hydrocarbon source rocks in the middle uplift area entered the hydrocarbon generation threshold is significantly earlier than that in other regions.At present,the Cretaceous hydrocarbon source rocks are in the dry gas generation stage,whereas the Eocene hydrocarbon source rocks are in the oil generation stage.The petroleum geology condition in the middle uplift is outstanding,indicating it to be a favorable hydrocarbon area.