四川盆地及周缘广泛发育六套海相、海陆过渡相及陆相页岩地层,五峰组–龙马溪组海相页岩是最有利的勘探开发层系,优质页岩厚度20~80米。目前,四川盆地下志留统龙马溪组海相页岩气工作已经进入大规模效益开发阶段,开钻井上千口,完钻井接近1000口。开展优质页岩精细预测,引导布井位置的优选,提高优质储层的钻遇率,是页岩气勘探——开发一体化的迫切需要。本论文以四川盆地Z地区为例,将基于全道集叠前反演应用于生产实践,预测页岩气水平井目标靶体储层厚度,指导水平井轨迹设计。结果表明:基于全CRP道集叠前反演技术充分利用了原始道集中完整的AVO信息,解决了目前页岩气优质页岩储层识别的难题,帮助划分页岩气的有利区,提高了页岩气水平井钻探成功率,降低了勘探开发成本。 Six sets of marine facies, marine-terrestrial transition facies and continental shale strata are widely developed in the Sichuan Basin and its periphery. The O3w~S1l1 Formation marine shale is the most favorable formation for exploration and development, and its high-quality shale is about 20~80 meters thick. At present, the Lower Silurian Longmaxi Formation marine shale gas in the Sichuan Basin has entered a large-scale profitable development stage. More than 1,000 wells have been drilled and nearly 1,000 have been completed. Carrying out fine predictions of high-quality shale, guiding the deployment of well positions, and increasing the drilling encounter rate of high- quality reservoirs are all urgent needs for the integration of shale gas exploration and development. This thesis takes the Z area of the Sichuan Basin as an example, and applies the pre-stack inversion based on the complete set in production practice to predict the reservoir thickness of the target body of a shale gas horizontal well, thereby guiding the design of the horizontal well trajectory. The results show that the pre-stack inversion technology based on the full CRP gathers makes full use of the complete AVO information of the original gathers, which not only solves the current problem of identifying high-quality shale gas shale reservoirs, but also helps to distinguish favorable areas for shale gas. While increasing the drilling success rate of shale gas horizontal wells, it also reduces exploration and development costs.
四川盆地及周缘广泛发育六套海相、海陆过渡相及陆相页岩地层,五峰组–龙马溪组海相页岩是最有利的勘探开发层系,优质页岩厚度20~80米。目前,四川盆地下志留统龙马溪组海相页岩气工作已经进入大规模效益开发阶段,开钻井上千口,完钻井接近1000口。开展优质页岩精细预测,引导布井位置的优选,提高优质储层的钻遇率,是页岩气勘探——开发一体化的迫切需要。本论文以四川盆地Z地区为例,将基于全道集叠前反演应用于生产实践,预测页岩气水平井目标靶体储层厚度,指导水平井轨迹设计。结果表明:基于全CRP道集叠前反演技术充分利用了原始道集中完整的AVO信息,解决了目前页岩气优质页岩储层识别的难题,帮助划分页岩气的有利区,提高了页岩气水平井钻探成功率,降低了勘探开发成本。
四川盆地,页岩气,优质页岩厚度,水平井部署,全道集叠前反演
Lijuan Huang, Ruining Li, Bo Jiang, Shiyu Zhou, Rong Yang, Zenghui Fan
Southwest Geophysical Research Institute of Eastern Geophysical Corporation, CNPC, Chengdu Sichuan
Received: Feb. 8th, 2022; accepted: Mar. 24th, 2022; published: Mar. 31st, 2022
Six sets of marine facies, marine-terrestrial transition facies and continental shale strata are widely developed in the Sichuan Basin and its periphery. The O3w~S1l1 Formation marine shale is the most favorable formation for exploration and development, and its high-quality shale is about 20~80 meters thick. At present, the Lower Silurian Longmaxi Formation marine shale gas in the Sichuan Basin has entered a large-scale profitable development stage. More than 1,000 wells have been drilled and nearly 1,000 have been completed. Carrying out fine predictions of high-quality shale, guiding the deployment of well positions, and increasing the drilling encounter rate of high-quality reservoirs are all urgent needs for the integration of shale gas exploration and development. This thesis takes the Z area of the Sichuan Basin as an example, and applies the pre-stack inversion based on the complete set in production practice to predict the reservoir thickness of the target body of a shale gas horizontal well, thereby guiding the design of the horizontal well trajectory. The results show that the pre-stack inversion technology based on the full CRP gathers makes full use of the complete AVO information of the original gathers, which not only solves the current problem of identifying high-quality shale gas shale reservoirs, but also helps to distinguish favorable areas for shale gas. While increasing the drilling success rate of shale gas horizontal wells, it also reduces exploration and development costs.
Keywords:Sichuan Basin, Shale Gas, Thickness of High-Quality Shale, Horizontal Well Deployment, Pre-Stack Inversion of Full Stack Gathers
Copyright © 2022 by author(s) and Hans Publishers Inc.
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我国的页岩气资源非常丰富,主要分布在四川盆地及其周缘地区上奥陶统五峰组——下志留统龙马溪组地层中。四川盆地下志留统龙马溪组海相页岩是目前中国页岩气发展的主要产层,水平井的箱体设计都是五峰组–龙马溪组优质页岩段(即水平井目标靶体) [
目前页岩气储层预测中,使用比较多的方法是常规叠前反演(是基于部分叠加数据体进行的)。基于部分叠加数据体的叠前反演,对CRP道集进行部分叠加。以地震道振幅的平均值作为该部分叠加剖面的振幅值 [
基于全道集的叠前同时反演是水平井目标靶体厚度预测的关键技术。全叠加CRP道集包含了较完整的AVO信息 [
基于全道集的叠前反演主要经过数据导入、道集修饰处理、层位标定、子波提取、模型构建、反演参数选取(反演参数QC)、反演、质控共8个步骤完成。全道集叠前同时反演前要对道集进行修饰处理:1) 对原始CRP道集进行修饰处理以获得高品质的叠前道集,修饰处理包括道切除、滤波、超级道集处理、非地表一致性静校正等;2) 利用层速度把CRP道集转化为角度域道集后方可进行叠前同时反演。我们首先采用切除来消除远偏移距道集上的噪声(见图1);利用带通滤波来消除剩余的低频噪声(图2);生成超级道集能够有效地压制随机噪声(见图3) [
图1. 切除前后对比图
图2. 滤波前后对比图
图3. 生成超级道集
图4. 非地表一致性静校正前后对比图
四川盆地Z地区龙马溪组处于深水外陆棚环境,沉积了大量富有有机质的黑色页岩(图5)。龙马溪组岩性主要为灰黑色粉砂质页岩、炭质页岩、硅质页岩夹泥质粉砂岩,龙马溪组地层自上而下颜色逐渐加深、砂质逐渐减少、有机质含量明显增高 [
四川盆地Z地区优质页岩段在纵向上主要分布在龙一1和龙一2亚段,储层与围岩在纵波速度、密度、纵横波速度比等方面都有差异,储层段较围岩具有低纵波速度、低纵横波速度比、低密度、高自然伽马、高TOC、高总含气量与高孔隙度特征 [
图5. W井岩性柱状图
图6. 龙马溪组地层划分
图7. 敏感参数分析
图8. 敏感参数分析
1) 建立工区,数据导入,测井资料分析:
首先收集、整理并合理的处理井资料;在构造解释层位的基础上精细解释层位,最后以1 × 1的网格调整目的层位,达到储层预测标准为止;将所需要的地震数据,层位数据和测井资料导入工区,对测井曲线进行分析和井间对比,必要时和测井解释人员一起对测井资料进行合理的调整 [
2) 道集修饰处理:
检查收集到的全道集(CRP)数据,根据需求进行道切除、滤波、超级道集处理、非地表一致性静校正等一些处理,对道集数据进行优化处理,提高全叠加道集数据的信噪比,达到精细储层预测对叠前地震数据的要求 [
3) 利用层速度把全道集数据转换为角道集数据,用于叠前道集反演。
4) 层位标定、子波提取、模型构建、反演参数选取(反演参数QC)。
5) 反演:在测井资料和地震层位的约束下,进行叠前弹性参数反演。
6) 质控:
质控一般分两步:首先是将我们的井旁到的反演数据与测井数据进行对比,两者趋势一致且差异较小的情况下,如果反演结果的纵横向变化合理,则认为反演结果大致可靠;再次,基于反演结果进行正演,生成一个合成道集,将合成道集与原始道集的振幅、频率和AVO特征进行对比,当误差道集趋于白噪时,认为反演结果可靠 [
完成基于全道集叠前反演完成后,得到高精度的弹性参数数据体(纵波阻抗、横波阻抗、密度)。图9是基于全道集的叠前同时反演得到的纵波阻抗和横波阻抗反演剖面,插入的曲线是对应的测井曲线。可以看出,井旁道反演结果与测井曲线吻合度高,特征一致,反演结果可靠 [
图9. WELLA纵波阻抗和横波阻抗预测剖面
图10. WELLB密度预测剖面
根据密度预测数据体,提取出密度小于等于2.61的采样点(即为测井响应分析得到的优质页岩储层段),乘以对应点速度,编制出龙马溪组优质页岩储层的厚度平面分布图(图11)。
实钻结果表明,利用我们的预测结果与钻井数据符合率较高,能够合理的引导水平井平台部署。预测的结果为水平井优选页岩气有利区提供了重要依据和保障 [
图11. 龙马溪组优质页岩厚度分布图
1) 基于全道集的叠前同时反演技术充分利用叠前道集中的AVO信息,能刻画出优质页岩储层内部特征变化,提高弹性参数的反演精度。此技术的关键在于对于叠前全叠加道集数据的优化处理。
2) 基于全道集叠前反演预测出优质页岩储层的空间及平面展布,预测精度高,为该区页岩气开发设计提供可靠依据,精确定位靶点位置是指导水平井准确入靶的基础。
黄丽鹃,李睿宁,蒋 波,周诗雨,杨 容,范增辉. 基于全道集叠前反演的页岩气优质页岩储层厚度预测Prediction of Post-Reservoir Thickness of High-Quality Shale Gas Shale Based on Pre-Stack Inversion of Full Stack Gathers[J]. 地球科学前沿, 2022, 12(03): 386-395. https://doi.org/10.12677/AG.2022.123040