Experimental Investigation of Formation Damage Induced by Completion in Dibei Tight Condensate Gas Reservoir

Dibei gasfield is a naturally fractured tight sandstone condensate gas reservoir in Tarim basin with low matrix permeability, and strong heterogeneity in natural fracture development. several stimulation methods, such as acidizing, acid fracturing and hydraulic fracturing were applied to improve production, but there are no ideal stimulation result achieved by sand fracturing and no evident correlation between production and stimulation scale. Formation damage caused by retrograde condensation and fluid solid deposition are taken into consideration.Based on the Dibei gasfield features of high condensate content, high pressure, high temperature, low porosity and low permeability, a series of experiments, such as fluid solid deposition, long core displacement and constant volume depletion were applied to evaluate the formation damage in retrograde condensation and the solid deposition at HPHT. The influence factors of retrograde condensation damage and the solid deposition damage is studied by Long core displacement and fluid solid deposition of inflow fluid and condensate gas.Two sets solid deposition damage experiments were carried out to detect the solid deposition damage by injecting drilling mud and formation water into reaction kettle filled with condensate gas respectively, and we found that there are some potential factors of the solid deposition damage when formation water mixed with the drilling mud. Meanwhile, two sets Long core displacement test were completed to investigate the impact of retrograde condensation damage induced by the fracturing fluid on the effectiveness of gas field fracturing. The retrograde condensation damage without fracturing fluid is 15.4% and the increment of retrograde condensation damage by fracturing fluid is only 5%. The constant volume depletion result shows lower level retrograde condensate loss and high condensate recovery degree. All evaluation experiment results reveal that retrograde condensation damage resulted by completion is not as serious as expected.The damage of retrograde condensation induced by the fracturing fluid is studied by long core displacement test in Dibei condensate gas reservoir. This paper has offered important reference for the damage evaluation method in the similar reservoirs.KeywordsThe damage by retrograde condensationLong core displacement testStimulationTight condensate gas reservoir