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寿阳区块煤层气田的水文控藏模式及控产特征

Hydrological control mode and production characteristics of coalbed methane field in Shouyang Block

  • 摘要: 地下水对煤层的补、径、排关系不仅影响着煤层气的富集程度,而且影响着煤层气井的产气特征。为查明水文地质条件对煤层气富集和产气的影响,以寿阳区块15号煤层为研究对象,基于排采水离子测试数据和地下水势,分析了排采水化学特征参数、地下水势与含气量关系;结合水文控气作用分析,提出了3种控藏模式。根据不同控藏模式下煤层气井的产水、产气曲线形态及成因机制,划分了6种控产特征,并提出了相应的开发建议。结果表明:水化学特征参数、地下水势与含气量相关性显著。即矿化度、变质系数越大,钠氯系数、碳酸盐平衡系数、地下水势越小,含气量越高。水文地质条件以水动力逸散、封堵、封闭作用控制着煤层气逸散和富集成藏;水动力逸散控藏区,低含气量是煤层气井低产的主控因素,开发风险高;水动力封堵控藏区产水量普遍大。其中水动力强、低渗透率地区,易出现高产水低产气井,不建议开发;供液能力强、低渗透率易出现中产水低产气井,储层改造效果决定了开发的可行性;较高渗透率地区易出现高产水中产气,应注意排采的连续性。水动力封闭控藏区产水量小,其中低渗透储层易出现低产水低产气井,应注意储层改造的有效性;渗透率好的地区,一般为中−高产气井,应尽量保持排采连续性,降低储层伤害。研究成果可为煤层气井位部署提供理论指导。

     

    Abstract: The relationship between groundwater replenishment, runoff and discharge to the coal seam affects not only the degree of coalbed methane (CBM) enrichment, but also the gas production characteristics of CBM wells. In order to identify the influence of hydrogeological conditions on CBM enrichment and gas production, the No. 15 coal seam in Shouyang block was used as the research object, and based on the ion test data of drainage water and underground water potential, the relationship between chemical characteristic parameters of drainage water, underground water potential and gas content was analyzed, combined with the hydrological control gas effect, and three types of reservoir control models were proposed. According to the water production, gas production curve shape and genetic mechanism of CBM wells under different reservoir control modes, six production control characteristics are divided, and corresponding development suggestions are put forward. The results show that: hydrochemical characteristic parameters and groundwater potential are significantly correlated with gas content. That is, the greater the mineralization and metamorphic coefficient, the smaller the sodium-chloride coefficient, carbonate equilibrium coefficient, and groundwater potential, the higher the gas content. Hydrodynamic force controls the escape and accumulation of coalbed methane by hydrodynamic dissipation, plugging and sealing. In the reservoir area controlled by hydrodynamic dissipation, low gas content is the main controlling factor of low production of CBM wells, and the development risk is high. In hydrodynamic plugging control areas, the water production of coalbed methane wells is generally large. Among them, strong hydrodynamic, low permeability prone to high water production and low production gas wells, not recommended for development; strong liquid supply capacity and low permeability are prone to medium water production and low production gas wells, the effect of reservoir reconstruction determines the feasibility of development. High production of water and gas is easy to occur in areas with high permeability, so the continuity of drainage should be pay attention. In hydrodynamic closed reservoir-controlling areas the water production of coalbed methane wells is generally small. Among them, low permeability reservoirs are prone to low water production and low gas production wells, so attention should be paid to the effectiveness of reservoir reconstruction; in the areas of high permeability reservoir, there are generally medium-high-yield gas wells. The continuity of drainage and production should be maintained as much as possible to reduce reservoir damage. The research results can provide theoretical guidance for the deployment of CBM wells.

     

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