强非均质致密砂岩气藏剩余气分布定量描述与挖潜对策--以苏里格气田苏11区块北部老区为例

Quantitative description of residual gas distribution in strong-heterogeneity tight sandstone gas reservoirs and potential tapping strategies:a case study of the old area of northern Su 11 Block in the Sulige Gas Field

鄂尔多斯盆地苏里格气田苏11区块北部老区经过十余年的开发,低产低压气井逐年增多、储量动用不均衡、剩余气分布复杂等问题越来越突显。为了改善其开发效果,在调研同类型气藏开发经验的基础上,应用复杂河流相砂岩储层精细刻画技术和地质建模、数模一体化剩余气评价技术,准确描述井间、层间剩余气的分布,然后在明确侧钻水平井、侧钻井和调层井选井选层技术界限的基础上,制订出具体的挖潜对策,指导了该区块现场挖潜工作。研究结果表明:①复杂河流相砂岩储层精细刻画技术可以实现单砂体级别的精细刻画,对优势储层进行定量描述,为河流相储层地质研究提供了模式指导;②“动态分析法+数值模拟法”天然气剩余储量评价技术精准描述了剩余气的平面和纵向分布特征,为下一步挖潜指明了方向;③苏11区块北部老区天然气剩余储量分布可划分为井网未控制型、层内非均质型及层间非均质型3种模式,针对井网未控制型优先考虑侧钻水平井挖潜,针对层内非均质型优先考虑侧钻井挖潜,针对层间非均质型则优先考虑部署调层井挖潜;④确定了侧钻水平井、侧钻井、调层井选区选井选层技术界限,在苏11区块北部老区已累计部署侧钻水平井5口、侧钻井8口、调层井79口;⑤截至目前,现场措施井有效率达100%,累计增产天然气1.01×108 m3。结论认为,基于该项研究成果所提出的致密砂岩气藏开发老区挖潜对策,取得了较好天然气增产效果,值得借鉴和推广。

After more than ten years of development in the old area of northern Su 11 Block in the Sulige Gas Field,some problems get more and more prominent,such as the increase of low-yield and low-pressure gas wells,uneven production of reserves,and complex distribution of remaining gas.In order to improve its development effect,it is required to accurately describe the distribution of remaining gas between wells and between layers by means of the fine characterization technology for complex fluvial sandstone reservoirs and the geological modeling-numerical simulation integrated remaining gas evaluation technology,after investigating the development experience of similar gas reservoirs.Then,after the technical boundaries of layers and well selections in sidetracking horizontal wells,sidetracking wells and layer-adjusting wells are defined,specific potential tapping strategies are formulated to guide the on-site potential tapping operation in this block.And the following research results were obtained.First,the fine characterization technology for complex fluvial sandstone reservoirs can realize the fine characterization in the level of single sandbody,quantitatively describe dominant reservoirs and provide model guidance for geological research of fluvial reservoirs.Second,the remaining gas reserve evaluation technology based on the dynamic analysis method and numerical simulation method accurately describes the lateral and vertical distribution characteristics of the remaining gas,and points out the direction of potential tapping in the next step.Third,the distribution of the remaining gas reserves in the old area of northern Su 11 Block can be divided into three modes,including uncontrolled well pattern types,intralayer heterogeneity types and interlayer heterogeneity types.For the uncontrolled well pattern type,priority is given to a sidetracking horizontal well for potential tapping.For the intralayer heterogeneity type,priority is given to a sidetracking well.And for the interlayer heterogeneity type,priority is given to a layer-adjusting well.Fourth,the technical boundaries of wells and layer selections in a sidetracking horizontal wells,sidetracking wells and layer-adjusting wells are determined.In the old area of northern Su 11 Block,5 sidetracking horizontal wells,8 sidetracking wells and 79 layer-adjusting wells have been deployed in total.Fifth,up to now,the efficiency of on-site measure wells is up to 100%and the cumulative natural gas increment is 1.01×108 m3.In conclusion,the potential tapping countermeasures for the old areas of tight sandstone gas reservoirs proposed on the basis of the research results achieve remarkable results in natural gas production increase and are worth popularizing and using for reference.