The Research And Application Of Emulsified Fracturing Technology For High Water Sensitive Reservoir

This dissertation mainly focuses on high water sensitive reservoirs in which large scale low permeability reserves were discovered in recent years. A lot of laboratory experiments and comprehensive evaluation have been carried out. The dissertation analyzed the outstanding features and stimulation difficulties of this kind of reservoir, proposed the corresponding countermeasures, and established a set of fracturing technology which is suitable for the high water sensitive reservoirs. The breakthroughs in both theoretical study and development technique application are as follows:(1) A set of pre-fracturing comprehensive evaluation technology was formed which is suitable for the high water sensitive reservoirs, and resolves the difficulties of less exploration data and pre-fracturing evaluation.(2) Two fracturing fluid systems named carboxymethyl guar gum & diesel emulsified fracturing fluid and high pour-point crude oil emulsified fracturing fluid were established, which could adapt to different water sensitive reservoirs.(3) Viscous fingering and two-pump-shutdown were used to control the fracture height and measure the fluid leak-off respectively. An optimal fracturing technology to high water sensitive reservoirs was formed based on the proppant slug profile optimization and slug injection of mixed particle sizes.(4) An online emulsification and real-time mixture technology was developed for the first time, which reduced cost and achieved green operation.(5) Fracturing flow-back control technology was formed, a set of flow-back parameters control software was developed, and flow-back rate and post-fracturing effect were enhanced.In Yitong exploratory area of Jilin Oilfield, the cumulative fracturing operations of emulsified fracturing are 74 wells and 98 layers. The success rate of fracturing operation is 100%.In Santanghu Basin of Tuha Oilfield, field tests are conducted on 15 wells by using emulsified fracturing fluid. The success rate of fracturing operation is 100%. The flow and flow-back ratio of the emulsified fracturing fluid is more than 40%, and the final flow-back rate is more than 60%. Geological efficiency reached 60%.Emulsified fracturing operations are performed on 12 layers of 5 wells in Haita Basin, and the range of flow-back ratio is 60.0%-96.0%. The maximum sand ratio is 27%-33%, and the average sand ratio is 18%-21%. Geological efficiency is 45.5%(28.4% in 2008).The established technology overcame the difficulties for high water sensitive reservoir stimulation. The application of this technology enhanced oil production of high water sensitive reservoirs and achieved a better understanding of the reservoirs. It provides favorable guarantee for the production increase, and also makes great contributions to the stableness of domestic oil and gas market and guarantee of reserve replacement of oilfields.