Stress Sensitive Evaluation Of Low Permeability Sandstone And Conglomerate Reservoir And Its Impact On Oilfield Development

Take MB oil field as the research object, from the glutenite reservoir characteristics, based on the analysis of the oil reservoir geology and development characteristics, we evaluate stress sensitivity of the low permeability glutenite reservoir. On the basis of experimental research and analysis, combined with porosity stress sensitive experiment and permeability sensitive experiment, around low permeability glutenite reservoir water-flooding development theory, we systematically carry out the reasonable research of development technology policy boundaries of glutenite reservoir. Using reservoir engineering method and numerical simulation means, we research and analyze the influence of stress sensitivity on low permeability glutenite reservoir with the development of water-flooding. The main research results include:(1) The WuErhe, BaiKouquan reservoir stratums are poor reservoirs with the principle of secondary pores, finely throat, low pore and low permeability.(2) This article uses porosity stress sensibility coefficient as evaluate method of porosity stress sensibility, porosity stress sensibility coefficient is established on the basis of the change of the pore compression coefficient, therefore it could describe porosity stress sensibility more accurately. The experimental results show that along with the increase of net overlying stress, the porosity stress sensibility of reservoir gradually weakened.(3) The results of glutenite reservoir permeability change rules experiment under changing confining pressure conditions show that reservoir has significant pressure sensitive effect, along with the increase of confining pressure, permeability got lower; along with the decrease of confining pressure, the permeability began to recover slowly, gradually rise, but less than the original value recovery, that is to say, the loss of permeability is irreversible due to stress sensitivity.(4) The effects of stress sensitivity on capacity is that in low bottom-hole pressure stage, it has greater influence on oil well productivity; and it’s relatively lower when it’s in high bottom-hole pressure stage. So it should be in smaller pressure differentials to produce low permeability reservoir while considering stress sensitivity. When bottom-hole pressure decreases by 5MPa, the volume of production of the two areas will decline about 20 percent. Analyzing different stress sensitivity of sensitive coefficient, it’s considered that along with the increase of stress sensitive coefficient, the reduction of oil well production will increase. While the stress sensitivity coefficient each additional is 0.02, there will be about 10 percent reduction of well production under the same bottom-hole pressure.(5) In order to study reasonable timing of water injection, an approach for calculating the reasonable water-flooding timing in consideration of the pressure-sensitivity effect was proposed on the basis of reservoir material balance principle and economic assessment. The result showed that MB oil field should be taken to the advanced water-flooding development approach, because the advanced water-flooding process could decrease the harmful impaction of pressure-sensitivity effect in the low-permeability reservoir. The reasonable advanced water-flooding timing is usually less than one year.(6) Through establishing stress sensitivity numerical simulator of low permeability glutenite reservoir, we conducted comprehensive evaluation for stress sensibility water-flooding for MB oil reservoir. The result of simulation and forecast shows that the effect of stress sensibility cannot be ignored, adopting advanced water-flooding could improve development effect. Throughout the whole forecast period, the effect of advanced water-flooding is obviously better than synchronous and hysteretic water-flooding, for advanced water-flooding has high oil production, small decrease, and long effective stable period. The advanced water-flooding makes reservoir maintain in strata pressure level, and establishes effective pressure flooding system.