INVESTIGATION OF THE PRODUCTIVITY PREDICTION MODEL OF THE ACID FRACTURING WELL CONSIDERING THE REAL GAS PVT

摘要

Acid fracturing has been widely used to increase oil and gas well productivity. However, the wormholes, emerging when fracturing, have a great effect on the deliverability of a gas well. Based on the influences of the real gas PVT variation on the well deliverability under formation conditions and the non-Darcy effects, a productivity prediction model of a finite conductivity vertical acid fracturing well in a low-permeability reservoir was established, considering the slippage effect, threshold pressure gradient, and stress sensitivity. The result shows that the gas well productivity with variation of the gas PVT parameters is higher than that with constant PVT parameters during the low-flowing bottom hole pressure. The variation of PVT parameters has a larger impact on the gas well productivity, which decreases with the increase of the threshold pressure gradient and the stress sensitivity coefficient and increases with the increase of the slippage factor. In the fracture design of the low-permeability gas reservoir, it is more important to increase fracture length than its conductivity. There is an optimum value of flow conductivity that exists under a certain fracture length, which increases with the increase of the fracture length. In addition, the wormhole length and permeability of the wormhole area have different impacts on the gas well productivity, and their mechanisms are different. The longer wormhole length has a negative impact on the gas production, whereas the permeability of the wormhole zone has a positive influence.