火山岩气藏三维地震描述——以徐家围子断陷营城组火山岩勘探为例

Three-D Seismic Description of Volcanic Gas Pool:A Case Study from Exploration to the Lower Cretaceous Volcanics in Xujiaweizi Fault Depression,Northern Songliao Basin

利用徐家围子断陷全三维叠前深度偏移资料进行火山岩体、火山机构相带、储层预测和含气性检测的综合分析,实现火山岩气藏精细描述。根据喷发方式,徐家围子断陷火山岩可划分为裂隙式、中心式和复合式3类:裂隙式喷发火山岩外部楔形、强振幅、低频、横向递变快,内部为断续反射、中强振幅、平行-斜交结构;中心式喷发和复合式喷发火山岩外部丘形、强振幅、低频、断续反射,内部为空白-杂乱反射。据此实现了火山岩识别。火山机构可划分为火山口-近火山口相带、近源相带、远源相带和火山沉积相带,在地震剖面上分别呈穹隆-丘状(内部反射杂乱)、断续层状、层状、凹陷-充填状。利用相干体分析技术实现了火山机构相带识别。根据井-震联合储层反演成果和地震衰减属性的含气性检测成果,有利储层预测结果与后期钻探结果的最大相对误差为17.0%,平均为10.2%,含气性检测结果符合率提高到75%,为火山岩气藏勘探提供依据。

Volcanic rocks, facies belts of volcanic edifices, reservoir prediction and hydrocarbon detection of Xujiaweizi fault depression are analyzed by using of full 3-D seismic data, and the detail description of the volcanic gas pools is made . According to eruptive types, the volcanic rocks of Xujiaweizi fault depression are classified into fissured type, central type and compound type. The volcanic rocks of fissured type have wedge outer shape with strong amplitude, low frequency and bad continuum. However, its inner characteristics are bad continuous reflection, middle-strong amplitude, parallel-diagonal structure. The volcanic rocks of central and compound type have mound outer shape with strong amplitude, low frequency and bad continuum. And their inner characteristics are blank- chaotic reflection. Volcanic edifices are divided into crater-near crater facies belts（CNCF）, proxy facies belt（PF）, distal faceis belt（DF） and volcanic-sedimentary facies belt（VSF）. The CNCF has mound shape and chaotic reflection. The PF has bed reflection. The DF has bed shape and good continuum. The VSF has filling structure and good continuum. And volcanic facies belts can be recognized by using of coherence cube technique. According to the results of well-seismic integrated reservoirs inversion and hydrocarbon detection of attenuation attributes ,the relative errors between reservoirs prediction results and new-well is decreased to 17. 0% （the average value is 10. 2%）. The accuracy of hydrocarbon detection is increased to 75%. All above provide foundation for exploration of volcanic gas pools.