基于测井资料的TIV地层水平地应力计算方法

A Logging Data-Based Calculation Method for the Horizontal TIV Formation In-Situ Stress

低孔低渗地层常具有TIV各向异性特征,准确计算水平地应力对该类储层的射孔和压裂设计至关重要。为了更加准确地计算TIV地层的水平地应力,针对该类地层的低压特征,优选Bowers法求取地层孔隙压力,然后利用阵列声波测井资料求取TIV地层的岩石力学参数(垂直与水平方向上的杨氏弹性模量和泊松比);同时考虑层理面产状对水平地应力的影响,改进了传统的Sn模型,建立了TIV地层水平地应力新计算模型。用新模型计算了鄂尔多斯盆地合水地区长6、长7和长8段TIV地层的水平地应力,计算结果与实测最大、最小水平地应力的最大相对误差分别为8.70%和7.86%,低于Sn模型的相对误差。研究结果表明,新模型计算的水平地应力更符合实际地应力纵横向分布的变化规律,可为致密油储层的水力压裂设计提供更可靠的参考依据。

Given the TIV anisotropy characteristics of low porosity/permeability formations,the accurate calculation of horizontal in-situ stress is essential for the perforation and fracturing designs of those reservoirs.In order to more accurately and effectively calculate the horizontal in-situ stress of a TIV formation,considering the low-pressure characteristics of such formation,the Bowers method was used to obtain the formation pore pressure.Then,the array acoustic logging data was used to obtain the anisotropic rock mechanical parameters(the vertical/horizontal Young’s modulus of elasticity and Poisson's ratio)of TIV formation.Considering the influence of bedding plane occurrence on horizontal in-situ stress,the traditional Sn model was improved and a new calculation model for the horizontal in-situ stress of TIV formation was established.The horizontal in-situ stresses of the TIV formations in the Chang 6,Chang 7 and Chang 8 sections of the Heshui area of the Ordos Basin were calculated by this new model.The maximum relative errors between the calculated and the measured maximum/minimum horizontal in-situ stresses were 8.70%and 7.86%,respectively,which were smaller than those of in-situ stresses calculated by Sn model.The results showed that the horizontal in-situ stress calculated by this new model was more in line with the variation laws of the vertical and horizontal distributions of the actual in-situ stress,which could provide a more reliable reference for the hydraulic fracturing design of tight oil reservoirs.