NUMERICAL WELL TESTING ANALYSIS OF PRESSURE CONSIDERING NON-UNIFORM DISTRIBUTION OF SKIN FACTORS IN FRACTURED WELLS

When conducting pressure test analysis on fractured wells in unconventional reservoirs, the fracture skin factor is usually considered as a single fixed value. However, due to the complexity of fracturing measures, the pollution level in the surrounding area of the fractures is not uniform, resulting in a very complex distribution pattern of formation pressure. Therefore, in order to accurately describe the pollution area of non-uniform distribution of fractures, from the perspective of the definition of fracture skin factor, the formula for determining the non-uniform distribution of crack skin factor was determined, and a corresponding numerical model was established the calculation. Different skin distribution patterns were considered to study the changes in pressure testing curves and pressure fields. The research results indicate that under the distribution pattern of the large center and small sides of the crack skin factor, the protrusion height of the transition section of the pressure testing curve is higher, the duration of the linear flow section is shorter, and the pressure drop is mainly concentrated at the root of the crack. Under the distribution pattern of small center and large sides of the crack, the protrusion height of the transition section of the pressure testing curve is lower, the radial flow occurs earlier, and the pressure drop is mainly concentrated at the center of the crack. By comparing and calculating on-site examples, the practicality of the model was further verified, providing a new application method for the evaluation of fracture pollution and pressure distribution in fractured wells. The obtained results are useful for the evaluation and understanding of unconventional oil and gas wells' production capacity.