FLOW MODEL FOR WELL TEST ANALYSIS OF LOW-PERMEABILITY AND STRESS-SENSITIVE RESERVOIRS

With the rapid development of the economy, low-permeability reservoirs have become much more important. Well tests work reasonably and effectively as a significant tool in developing low-permeability reservoirs. Since most low-permeability formations are stress sensitive, permeability and porosity are considered as functions of effective stress in many well test models. However, the stress sensitivity of pore compressibility has not been taken into consideration. In this paper, by introducing the concept of a pore compressibility modulus, a new well test model is established for low-permeability stress-sensitive reservoirs, in which all permeability, porosity, and pore compressibility are pressure dependent. The model is solved by both analytical and numerical methods. In addition, another model that considers wellbore storage and the skin effect is built and solved to calculate and analyze type curves. The errors caused by constant pore compressibility are also discussed. The research results can be used as a theoretical basis for well-testing interpretation and productivity evaluation in low-permeability and stress-sensitive reservoirs.