Oil reserves of the thin heavy oil reservoirs are estimated to be over 400 billion barrels. The recovery factor of waterflooding in these reservoirs is as low as 10−20% due to the high oil viscosity and correspondingly unfavorable mobility ratio. In addition, the commonly used thermal recovery methods are also unsuitable in such formations due to the significant heat loss to the adjacent formations. Thus, it is urgent to find an efficient and economic enhanced oil recovery (EOR) method to maximize the recovery factors in the thin heavy oil reservoirs. In this study, the feasibility of polymer-enhanced foam (PEF) flooding for the thin heavy oil reservoirs is investigated using the micromodel and core-flood experiments. The micromodel experiments show that foam quality has significant effects on the resistance factor and heavy oil recovery of the PEF flooding, where the displacement front of a low-quality foam case is more even than that of a high-quality foam case and surfactant−polymer (SP) flooding case. Core-flood tests further reveal that there is an optimal slug size under the experimental conditions, and the heavy oil recovery of PEF flooding is 23.9% higher than that of SP flooding when using the same slug size. Finally, a field-scale reservoir simulation is conducted, and the results show that after initial water-flooding in thin heavy oil reservoirs, the recovery factor achieved by the PEF flooding is 11.7% higher than that of the SP flooding and 21.4% higher than that of the continuous water-flooding process.

China owns the world's largest shale gas reserve and is the third country gaining shale gas breakthrough in the world besides the North America. Fuling in Sichuan basin is the first industrially exploited shale gas play in China. Fuling shale gas wells gain good production performance, and the gas rate of some wells are as high as 0.6 million m 3 during production test period. However, we still haven't get good understanding of SRV, one vital indicator to evaluate the performance of hydraulic fracturing in Fuling shale gas play.Production rate and pressure transient analysis by rate normalized pressure (RNP) and rate normalized pressure derivative (RNP') method is adopted. The SRV of the pilot wells in Fuling shale gas play is estimated from the boundary dominated flow in the RNP and RNP' log-log interpretation plot. In order to quantify the influence of parameters on SRV, statistical analyses are conducted on fourteen parameters categorized by three kinds including formation, stimulation, and well parameters.Results show that the parameters are angle between horizontal lateral and minimum stress direction, TOC, absolute open flow (AOF) potential, cumulative gas in first three months, injected fluid volume, porosity, injected fluid volume per stage, fractured clusters, fractured stages, injected proppant volume, flowback recovery in first three months, injected proppant volume per stage, proppant concentration, and horizontal lateral length sorted by the influence on SRV in descending order. The first five parameters have relative strong correlation with SRV. High TOC, porosity and cumulative gas production in early days are good indication of high SRV. Shale gas wells with horizontal lateral paralleled to the minimum stress direction can achieve highest SRV. The other nine parameters, especially proppant concentration and horizontal length show very weak influence on SRV.The negative correlation of proppant concentration on SRV may have been caused by ineffective fractures (networks), and a positive correlation can be achieved by detailed research of geology and engineering Љsweet pointsЉ and improved hydraulic fracturing techniques to control fracture propagation. The relationship between SRV and flowback recovery may have been disturbed by offset well's interference during hydraulic fracturing and production.

China is believed to own the world's largest shale gas reserve and is the third country to exploit shale gas breakthrough in the world. Fuling gas play in Sichuan basin is one typical shale gas reservoir in China gaining good production performance, and the absolute open flow capacity (AOF) of some wells reaches as high as 1.5 million cubic meters per day. However, we still haven't get good understanding of AOF to evaluate the producing potential and performance of hydraulic fracturing in Fuling shale gas play. In order to quantify the influence of parameters on AOF, statistical analyses are conducted on fourteen parameters including formation porosity, total organic carbon (TOC), injected fluid volume, injected proppant volume, injected fluid volume per stage, injected proppant volume per stage, proppant concentration, fractured stages, and fractured clusters, horizontal lateral length, angle between horizontal lateral and minimum stress direction, cumulative production in the first three months, stimulated reservoir volume (SRV) and flowback recovery in the first three months. Results show that six parameters including cumulative gas in first three months, angle between horizontal lateral and minimum stress direction, SRV, TOC, porosity and injected fluid volume show relative strong correlation with AOF with coefficient bigger than 0.50. The influence of the other nine parameters on AOF is very weak, and the coefficient between AOF and water flowback recovery in early days is even as small as 0.11. AOF is negatively correlated to three parameters including proppant volume per stage, proppant concentration, and angle between horizontal lateral and minimum stress direction. The negative influence of proppant concentration on AOF may have been caused by ineffective fractures (networks), and a positive correlation can be expected if proppants are injected into "sweet points" that meet the geology and engineering requirements and improved stimulation techniques with better performance of fracture propagation control. The angle between horizontal lateral and minimum stress direction is suggested to be less than 20° in order to get bigger AOF. AOF is positively correlated to the other eleven parameters. High TOC, porosity, injected fluid volume are good indication of high AOF.