Reservoir Pollution Analysis And Treatment Technology Of Yancheng Formation In YT Condensate Gas Reservoir

Yingcheng Formation, Yingtai gas field, a typical volcanic condensate gas reservoir with tight porosity and ultra-low permeability, mainly use fracturing to obtain the production. In the early development period, the production is high at first, then decrease sharply after a few time for insufficient energy supplement. After shutting in for pressure recovery, the well product no gas but condensated oil and accumulate liquid. Therefore, it is essential to take a deeper study in reservoir damage, explicate the causes of damage, next tackle problems like this, then remove the damage and finally recover the production.Research the status quo in gas formation damage mechanism, evaluation methods and blocking technique. After compared with those situations, Yingtai gas field should be evaluated pointedly. This study should rely mainly on laboratory experiments while take theoretical analysis, for researching the damage factors and treatment measures, subsidiary. To analyze the potential damage factors of this field, experiments like mercury injection curve, casting thin sections, SEM, X-ray diffraction, spectrum, and chromatographic should be taken. Our study will focus on the liquid phase damage. The evaluation is based on experiment, such as the P-T phase diagram, constant volume depletion experiment, isobaric expansion, APTi, and indoor water-lock damage evaluation. Based on the current damage factors, we should build a module to simulate the process of removing damage factor through acid and surfactant solution, then select an optimal acid system, next get the most fitable surfactant solution and acid craft by evaluating and comparing, optimize construction parameters, and finally foster a series of compound acid plugging relief scheme.After the former experimental and theoretic analysis of the damage principles and relevant plugging relief technology, the basic results are illustrated as follows.Depart from the nature attributes of this reservoir in contemporary situation, the main problem is the water blocking damage, which is caused by leading into the outer incompatible fluent and invading formation water during the former operation. What’s more, these liquids will make further damage, which may lead to formation cooling down, retrograde condensation damage and damage from fracturing liquid to hydraulic fracture. Water blocking damage, classified middle damage, mainly exists in the bottom nearby filtration zone. There is no retrograde condensation damage. This kind of damage, classified middle and lower, concentrates in the middle of the reservoir. The closing of fracture and the plug cause by fracturing fluid residue will reduce hydraulic fracturing fluid residue. Comprehensively considering various factors, we can draw a conclusion that water lock effect and retrograde condensation damage are more serious.After comparing and selecting composite acid fluid, which is based on lifting solid plugging and extending throat by retarded acid, lifting liquid damage, increasing liquid evaporation, reducing flow resistance by a composite surfactant solution, we can optimize acid fluid system7%HC1+2%HF+5%YJS-1+2%XN-HS-1+1.5%XN-TW-4+1.5%XN-ZP-l+2.5%XN-NW-1&anti dilution surfactant solution system1%XN-BH-2+20%XN-YJ-1+79% methanol. To uniform acid distribution, we will consider fiber temporary plugging technology. What’s more, construction parameters optimization will be used to reach the best result.