Advanced Materials Research Vols. 361-363

Abstract: Acidizing radius design is an important determinative factor for the economic benefit of acidizing. According to theoretical derivation on Darcy’s formula, the theoretical models of stimulation ratio and optimum acidizing radius for conventional injection well and fractured injection well are obtained. With the example of Hailaer Oilfield, the optimum acidizing radius of different types wells is obtained. This design model is applied for 7 wells in Xinanling Group of Hailaer Oilfield. The results of field tests indicate the design model is practical and can also be used to guide the acidizing design for other sandstone reservoirs.

Abstract: JYC polymer microsphere emulsion was synthesized by inverse emulsion polymerization. In order to explore the expansion mechanism of polymer microsphere, the variation of JYC sizes were detected. Through physical simulation experiments, the regulation of fraction flow and the result of displacement in heterogeneous physical simulation were measured. The results showed that the size of JYC microspheres swelled and increased in water at the reservoir temperature. After 60 days maintenance , the microspheres emulsion had the best dispersion and the property of expansion was prone to stability. Moreover, The appropriate injection concentration of JYC microspheres was 3000mg/L. JYC microsphere emulsion could improve the displacement efficiency of high permeability layer effectively, and expand the swept volume of low permeability layer, and enhance the ultimate recovery in different permeability ratio reservoir models.

Abstract: The steam flooding is one common way used to enhance oil recovery of heavy oil reservoir. It is difficult to use conventional treatment on steam flooding analysis because of numerous effective factors, complex relationships and no certain mapping relation among those factors. This paper applies grey relationship method to analyze correlative degree of the factors which effect on steam flooding, and then selects steam absorption effect as the comparative indicator, finally gets a sort of steam flooding effect of different parameters. Each correlation degree has a good match with steam flooding effect, and the higher of correlation degree the better of steam flooding effect. Grey relationship is an effective, fast and accurate method for appraising steam flooding effect.

Abstract: As one of the most important reservoir parameters, irreducible water saturation, S_wir, is a key parameter in evaluating multi-phase flow, as well as its importance in defining oil in-place. Residual oil saturation, the target of tertiary recovery, is also a function of S_wir. In traditionally, S_wir is determined by conducting capillary pressure experiments, requiring considerable resources and long time periods, with the consequence of a limited number of core plug evaluations for a particular reservoir. Thus, the estimation of S_wir with mathematical models is developed in recent years. The study reported in this paper uses artificial neural network to determine S_wir. The optimal model is chosen among 25 simulations, subtilizing different combinations of hidden layer nodes and activation functions for the hidden and output layers. Its performance is compared with other conventional models, demonstrating the superior performance of the proposed S_wir prediction models.

Abstract: Polymer microsphere is a deep profile control agent which has been developed in recent years. Microsphere’s excellently elastic property makes it possible to be injected, or to penetrate deep into formation, and plug high permeable layers. Many laboratory investigations have been carried out on polymer microspheres by researchers, and field tests also have been done in some oilfields. The laboratory and field test results show that polymer microspheres can plug pore throats effectively, decrease permeability of high permeable channels, thus force injected water to change it’s direction and enhance water-flood sweep efficiency. In this paper, based on the mechanisms of profile modifying and plugging of polymer microsphere, Streamline models have been build abstractly to simulate the profile controlling progress of polymer microspheres, observe the transformation of streamline field, and analyze its impact on the pressure of water injection wells and performance of oil wells. In the end, the mechanisms of profile modifying and plugging of polymer microspheres have been interpreted based on the streamline field.

Abstract: In view of the complicated issue that how to improve the cementing quality of the second interface in cementing engineering, experimental and theoretical research on slag MTC slurry improving the quality of the second interface was carried out in the paper. Experimental study shows that slag MTC and mud cake can achieve overall cementing; the volume shrinkage ratio of slag MTC is far less than the cement slurry system; and the strength of slag MTC cannot be affected by the presence of mud cake and is greater than low-density cement slurry. Theoretical analysis shows that the alkali activator and Ca(OH)₂ produced by hydration can react with SiO₂ which exists in mud cake and dead mud to get C-S-H gel with a low ratio of calcium to silicon, and improving the quality of the second interface. The study on the chemical shrinkage ratio of the products of slag MTC hydration was made by using the method of chemical analysis, and low-shrinkage mechanism of MTC was revealed. The results show that mud cake solidification, dead mud solidification and low-shrinkage ratio are fundamental to improve the cementing quality of slag MTC and formation.

Abstract: High density brine drilling fluid has been widely applied in the high pressure and complex oil and gas fields. Effectively controlling high density brine drilling fluid loss is an important factor for reducing the reservoir damage and keeping well stability. Base on general drilling fluid formulations，the affecting factors of filtrate loss of high density brine drilling fluid were analysed through mass laboratory experiments. The results show that the main fctor was the content of caustic soda and bentonite, secondly the density and the shape of adding product. The combination of adding product is one of effective method to control the filtration property of high density brine drilling fluid. The results will provide reliable foundation for successful field application.

Abstract: The technical problems existing in deep well drilling are becoming more and more predominant during the exploration and development of oil-gas field. The poor formation drillability, low drilling rate and complicated pressure system cause the underground accidents frequent, extend well construction cycle, and make the cost of the project much higher. Therefore, it is urgent to develop new technologies to improve the efficiency of the exploration and development in deep unconventional oil-gas reservoir. The particle jet technology is a new energy-saving way which has a broad application prospect. It can take the way of sucking in particles in annulus space to cycle use the particles, and promote the drilling rate. The feasibility of particle jet as a drilling medium is verified by the theoretical and experimental study, which provides the basis for the design of particle jet tool.

Abstract: The oil-water interfacial tension measurement and enhancing water displacement recovery experiment were carried out, and the effects of various parameters such as category of surfactants, anionic Gemini surfactant concentration, water medium salinity, core permeability, polymer and non-ionic surfactant on anionic Gemini surfactants enhancing water displacement recovery were investigated in detail. The results show that surfactants category is different, its enhancing water flooding recovery efficiency is different, and effect of enhanced oil recovery is consistent with surfactant ability to reduce oil-water interfacial tension. The anionic Gemini surfactant AN12-4-12 is the best in enhancing water flooding recovery efficiency, because it can reduce the oil-water interfacial tension to 5×10^-3 mN•m^-1. Increasing the concentration of AN12-4-12 is favorable to enhance water displacement recovery. Such as when injecting 0.5PV solution containing 800mg•L^-1 AN12-4-12, enhancing water displacement recovery is 11.67%. AN12-4-12 has good adaptability to different salinities (5~25×10⁴ mg•L^-1) and low permeability reservoir in improving water displacement recovery. Adding non-ionic surfactant ANT into AN12-4-12 solution can further reduce oil-water interfacial tension and enhance water flooding recovery efficiency. For example, injecting 0.5PV surfactant solution containing 400mg•L^-1 AN12-4-12 and 100mg•L^-1 can enhance water displacement recovery of 10.7%.

Abstract: Limited entry fracturing technique is an effective method to stimulate low-permeability reservoirs. Especially for thin-interbedded reservoirs, this technique can, to a large extent, save fracturing operation cost and improve effectively stimulation degree of oil layers. In order to get targeted operations, various influence factors should be taken into account, to further optimize limited entry fracturing frame. Low-permeability thin interbedded reservoirs being featured with low permeability, multiple and thin layers, the numerical simulation method is applied to analyze the effect of perforation number and formation parameters, including minimum principal stress, pay thickness, permeability and porosity, on entry flow rate and fracture geometries. Through simulation, we find: the higher minimum principal stress, which is the main factor affecting proppant length, the shorter the proppant length; the thicker the pay zone or the more the perforation number, the larger the proppant width, while pay zone thickness and perforation number are the main factors affecting proppant width; the more the perforation number, which has the largest effect on proppant height, the larger the proppant height. Nonetheless, permeability and porosity has minor effects on fracture geometries.