油气田开发过程中的压力拱效应

 与矿山开采类似,油气开采时,储层和上覆岩层中会产生不均匀变形,从而在上覆岩层中形成压力拱。本文对油气开采时,储层和上覆岩层的变形特征进行了总结,利用现场实例说明了压力拱效应在油气开发过程中的存在性,同时对压力拱的表征参数以及计算方法进行了总结。提出了如果低渗和致密储层忽略压力拱效应,将会夸大应力敏感对储层开发特征的影响,同时导致该类储层开发策略的错误制定。对于该类储层,压力拱将会使得上覆岩层的部分重量传递到外围岩层中,有效地防止储层进一步变形,部分消除应力敏感的影响。压力拱将随着压降漏斗半径的增加而不断地向外扩展,可以增大压降漏斗内外裂缝的导流能力,从而提高油气井的产量和采收率,因此压力拱比较大的低渗致密储层可以适当放大生产压差。

Stress Arching in the Development of the Oil and Gas Reservoirs

Similar to the situation in the mining engineering, there will be a non-uniform deformation in the reservoir and the overburden during the development of oil and gas from underground. A stress arching will occur in the overburden due to this deformation. This deformation is analyzed in this paper and the features of the stress arching are illustrated with field examples. The stress arching ratio is used to describe the degree of the stress arching. The stress arching effect cannot be neglected during the production, otherwise the stress sensitivity will be exaggerated and unreasonable measures will be taken during the development of the low permeability and tight gas reservoirs. For these reservoirs, a part of the weight of the overburden is transferred to the non-formation (i.e sideburden) though the stress arching, which can protect the formation from deforming and eliminate the influence of the stress sensitivity. The range of the arching will increase with the increase of the pressure conductive ability and it will enhance the nature fracture conductive ability inside and outside the arching to improve the productivity and the recovery factor. Therefore, it is possible to use a large pressure drop to develop the low permeability and tight gas reservoir with a large stress arching ratio.