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The Sulige gas field is a typical low-pressure low-permeability tight sandstone gas reservoir. The reservoir has poor seepage capacity, strong heterogeneity, high mineralization of formation water and extremely scarce water resources on the site. These unfavorable factors have brought great difficulties to the on-site mining process. Now, a nano-composite green environmental protection slick water fracturing fluid system CQFR can be quickly dissolved because of the larger specific surface area, and the small molecular size makes the damage to the reservoir less than 5%, and the average drag reduction effect can reach more than 73%. It can quickly and well dissolve and maintain performance under high salinity conditions and fracturing flowback fluids. It responds well to the complex reservoir conditions on the construction site and makes the flowback fluid recyable, which greatly reduces the consumption of water resources on the construction site and effectively improves the construction efficiency and economic benefits.

Great challenge of the ultra-heavy oil recovery via cold approaches is attracting the increasing worldwide efforts. Here, we reported a microbial strategy with using the heterocycles-degrading and biosurfactant-producing Pseudomonas strain for heavy oil recovery without thermal energy input. To validate it, we initiated the bacterial evaluation of anaerobically heterocycles degradation and biosurfactant production under CO2 and N2 conditions. Results demonstrated that the CO2 can significantly facilitate the anerobic degradation and influence the yield and diversity of biosurfactant. Structural identification of the biosurfactants by HPLC-MS showed that the di-rhamnolipids and lipopeptides (iturin and fengycin) were respectively accounted for more than 80% and 60% under CO2 condition when fed with carbazole and dibenzothiophene. Degradation of heavy oil under CO2 condition made the better performance on the oil viscosity reducing, the surface tension reducing, emulsification, and oil degrading rate than that under N2 condition. Huff-puff field trials in Jilin oilfield successfully demonstrated that the cumulative oil production was increased from 48 tons to 566 tons with the effective period of more than 9 months, and the viscosity of the produced oil was significantly decreased by 50–65%. These results suggested that this green strategy was promising and economical to the oil recovery for the ultra-heavy reservoir where is easily accessible to CO2.

Conformance control by using the polymer gel is an important stimulation technique of heterogeneous oil reservoirs. After operation of the conformance control, the water channeling of heterogeneous oil reservoirs can be plugged, which can force the follow-up injected water to divert into the area with high oil saturation. Thus, under the action of water injection pressure, the polymer gel is deformed. Because this is a long-term process, the ability to resist the long-term deformation and resist damage of polymer gel is important for the long-term plugging effect. However, there are few reports on the effect of long-term rheological characteristics of the polymer gel on its plugging ability. Therefore, it is of great significance to study the rheological characteristics of the polymer gel under the long-term action of a stress, which can be used to accurately predict the effective period of plugging the water channeling. In this paper, taking the Hook body and the viscous pot as the basic elements, and considering the Maxwell model and the Kelvin model as the basic models, a combined viscoelastic mechanical model of the polymer gel is established, which can be used to simulate the creep deformation of polymer gel. At the rheological damage stage of the polymer gel, the strain is increased exponentially and the mechanical parameters is decayed exponentially with time. By introducing the damage variable, based on the stress - time equivalence principle of polymer materials, the time of creep fracture of the polymer gel can be accurately calculated. Since then, the polymer gel is started to break obviously and lost its ability for plugging. This study can provide an important guidance to optimizing the scheme of conformance control and predicting the validity period.

Microbial enhanced oil recovery has been well acknowledged and becoming an advanced technology for oil recovery. Compared with current techniques, a newly technical strategy of the in-situ heavy oil gasification to methane for oil viscosity reduction was proposed and successfully proved via enriching the methanogenic consortia from the brine of oil reservoir with heavy oil as carbon source. During 200days anaerobic culturing, 2.34g of heavy oil was degraded coupling with 1514μmol of methane production. Phylogenetic diversity analysis showed that the enriched consortia composed with sequences affiliated with the Firmicutes, Proteobacteria, Deferribacteres and Bacteroidetes. The recovered archaeal phylotypes were close to the Methanobacteriales and Methanosarcinales, which could convert the produced small molecules (formic acid and acetic acids) to methane. The viscosity of the degraded heavy oil was reduced by 72.45% at 20MPa after the dissolution of the produced methane. Core flooding tests finally showed that the oil degradation and methane production by the enriched methanogenic consortia made 14.7% of the tertiary enhanced oil recovery. These results demonstrated a promising and practical strategy of microbial technology on oil recovery by activating the methanogens in heavy oil reservoir.

Because it provides favorite ancillary support in terms of technology research and tools test, full-scale simulator for Drilling and Producing is still the focus for overseas researches. The test capability for full-scale simulator represents the level of development for national petroleum exploration and development. That the increasing efforts on unconventional oil & gas and deep water exploration brings new challenges to theory and technology for oil-gas exploration, so the full-scale simulator provides an intermediate bridge for theory and technology innovation. Following the tracks of the development of full-scale simulator, the overseas and domestic classify and development of full-scale simulator was analyzed, and identifying the main technical bottlenecks faced during it establish. This paper describes the development of key technologies for wellhead loading system, wellbore simulation technology and test monitoring system. On this basis, the research prospect for the full-scale simulator was forecasted.