Chemistry and Technology of Fuels and Oils最新文献

Oil and gas occurrence characteristics and seepage characteristics of tight reservoirs are the key to production. CT technology can monitor displacement and advance seepage front in time In this chapter, NMR experiments of spontaneous imbibition and CT monitoring experiments of differential pressure displacement are carried out for dense conglomerate to clarify the law of two-phase seepage. The results show that in spontaneous imbibition, the fluid circulation in the pore of tight glutenite is high, and there is no micro-fracture The pore volume of clay minerals with high content increases when exposed to water, which improves the imbibition recovery ratio However, the highly heterogeneous gravel distribution increases the complexity of seepage path and thus enhances the imbibition recovery ratio. The strong heterogeneity of sandy conglomerate leads to the formation of preponderant passages in seepage In the early stage of displacement, the water flooding effect is poor and a large amount of water accumulates With the increase of displacement time, there is no obvious change in oil saturation at both ends of the middle part of a large number of water rock samples The oil saturation is lower at both ends and higher in the middle.

The development of tight oil sandstones in the Extension Formation in the southwestern Ordos Basin and the mode of crude oil migration is a hotspot. A large number of geochemical experiments and computational methods were used to systematically study the crude oil transport characteristics of the Yanchang Formation in the Huaqing area. The results show that four typical types of inclusions are developed in the Yanchang Formation: inclusions in quartz fissures, inclusions in quartz colluvium and large rims, inclusions in calcareous colluvium, and inclusions in sodium feldspar. There are two peaks in the homogenization temperature of the inclusions: 80-100°C and 120-130°C. The Chang 6 and Chang 8 reservoirs in the Huaqing area have experienced the process of densification while forming reservoirs, and the physical properties of the sand body reservoirs during the maximum hydrocarbon discharge period are good, which is an effective channel for oil and gas transportation. The minimum oil column heights for oil and gas transportation in Chang 6 and Chang 8 Members are 7.48m and 15.68m, respectively. Proximity vertical transportation is an important mode of crude oil transportation and aggregation in the Yanchang oil group in the Huaqing area. The physical properties of crude oil in Huaqing area are good, showing low density, low viscosity, low freezing point and good fluidity. The hydrocarbon source rocks of the Chang 7 Member were transported under excess pressure and buoyancy along channels such as cheese root networks, connected sands and microfractures, and thus large composite lithologic reservoirs were formed in the Chang 6 and Chang 8 Members.

The installation of a surface conductor in deepwater jet drilling is crucial for offshore oil and gas development. This study investigates the interaction between the surface conductor and subsea soil during injection drilling. A simplified model using ABAQUS finite element software analyzes the damage effect of the water jet on the soil and simulates the mechanism of soil body damage under different parameters. The mechanical behavior of the soil and conductor during installation is examined, and the load-bearing characteristics of the soil are analyzed. Sensitivity analysis of factors such as injection displacement and bit extension reveals their significant influence on conductor installation. The findings provide insights into the drilling process and contribute to ensuring the stability of the wellhead in deepwater drilling operations.

Horizontal well fracturing technology is an important way to improve the oil recovery efficiency of low-permeability reservoirs. Aiming at a certain test area on the edge of Daqing oilfield, a simulation conceptual model is established using CMG reservoir numerical simulation software. The influence of engineering parameters such as the number of fracture clusters, fracture half-length, fracture permeability, production pressure difference on the peak daily oil production is analyzed. Moreover, the gray correlation method is used to analyze the influence of the above factors on the peak daily oil production. Using key factors as variables in the regression model, a mathematical prediction model for daily oil production peak is established. The findings should make an important contribution to the oil production peak prediction.

When the pile driving operation of the jacket platform is carried out, the depth of the steel pile into the mud is not enough or the maximum penetration depth of the steel pile is not the expected bearing layer, which will make the bearing capacity of the platform pile foundation insufficient, cause the platform to be unstable and cause safety accidents. In this paper, the energy conservation relationship in the process of pile sinking is analyzed and discussed from the calculation theory of hammering work and internal force work. Combined with the soil data of field engineering, the penetration of pile sinking of jacket platform is calculated and theoretically demonstrated. Through the above in-depth calculation and analysis, the variation law of penetration with formation depth is obtained. Finally, the control suggestions of pile sinking operation of jacket platform are obtained, in order to provide reference for engineering operation.

In this study, the pore structure and oil-water phase seepage characteristics of sandstone reservoirs of the Yanchang Formation in the Ordos Basin were deeply analyzed. Through scanning electron microscopy observation, oil-water phase percolation experiments and nuclear magnetic resonance (NMR) experiments on 30 core samples, the pore structure was categorized into uniform macroporous, striated, microfractured and dense types. The experimental results show that the uniform macroporous type pore structure shows the strongest seepage capacity, and its ratio of liquid-measured to gas-measured permeability is 0.724 on average, while the dense type pore structure has the weakest seepage capacity, and the ratio is 0.091 on average; NMR T2 spectral analysis reveals that the cores with different types of pore structure show significant characteristic differences in the water-driven oil drive process, especially in the substitution of oil in the macroporous and micrometer pore In particular, the oil substitution in large pores and micron pores is remarkable, that is, the oil-water seepage process and the response of seepage and suction of cores with different types of pore structure are obviously different, which is a better way to study the characteristics of oil-water seepage and distribution of oil and water; the uniform macroporous type and the striptype pore structure are more effective in oil-water two-phase seepage, and the microfracture type and the dense type are relatively poor. This paper provides a basis for the exploitation of tight reservoirs in the study area, which is of great theoretical and practical significance for optimizing the oilfield development strategy and improving the efficiency of oil and gas exploitation.

The tight sandstone reservoirs in the Sulige Gas Field have complex pore structures and gas-water distribution, and the water production law in the complex gas-water distribution areas has not been clarified. The water production of gas wells in different regions varies greatly, and the water production of gas wells seriously affects the efficient development of natural gas. In order to improve the benefit of gas field development, this study takes stress-sensitive effects, gas-water immiscibility, and constant production conditions of gas wells under a certain gas-water ratio Rgw as constraints, and considers the fluid seepage as an isothermal seepage process, an evaluation model of the productivity of a theoretical water-producing gas well and a relative permeability model of the gas phase are constructed. Moreover, the influence of water production on the degree of pressure drop, gas well productivity, and gas well recovery was systematically analyzed. This study shows that when the water-gas ratio of gas wells is less than 1, 1-2, 2-3, 3-4, 4-5, and greater than 5, its influence on productivity is less than 40%, 52%, 50%, 58%, 61%, 65% and greater than 65%, respectively. The average water-gas ratio of the water-producing gas wells in the Sulige Gas Field is 1.27 m³/10 ⁴ m³. The effect of water production on recovery is compared with the case of no water production: for water-producing gas wells, the recovery rate of Type I wells is reduced by 8.45%, that of Type II wells is reduced by 9.58%, and that of Type III wells is reduced by 11.54%.

In order to improve the recovery rate of tight glutenite horizontal wells in the Baikouquan Formation in Mahu Sag, geological models were constructed through three aspects: structural modeling, lithofacies modeling, and attribute modeling; through rock mechanics parameters, in-situ stress direction, and vertical direction. Stress, pore fluid pressure, maximum horizontal principal stress, minimum horizontal principal stress to construct a one-dimensional in-situ stress model, combined with imaging logging wellbore wall caving and induced fractures to determine the in-situ stress direction to simulate the three-dimensional stress direction in the study area, using finite element method to simulate and The objective function fits and inverses the distribution of the three-dimensional in-situ stress field. Finally, comprehensive reservoir parameter characteristics and engineering parameter characteristics are used to predict the “sweet spot” of the study area. The results show that there are three types of sweet spots in the glutenite in the Mahu Depression: Type I sweet spots are good reservoirs with good oil content, high oil well production, and good reservoir engineering compressibility; Type II sweet spots are followed by oiliness and oil well production; Type III The sweet reservoirs have just reached the lower limit of the oil layer standard, mainly poor oil layers. The research results provide a reference for the development of Baikouquan tight glutenite in Mahu Sag.

Shale gas, as an important unconventional oil and gas resource, its efficient development can alleviate the current severe energy demand situation. However, the water absorption and expansion characteristics and hydration effects of shale pose a great threat to the drilling safety of shale, mainly wellbore stability. Therefore, based on mechanical property experiments, the influence of hydration expansion on the mechanical property parameters of brittle shale was analyzed, and an evolution model of the mechanical property parameters of shale with hydration expansion was constructed. In addition, a finite element model for numerical simulation of wellbore stability in shale formations was established, and the effects of factors such as the addition of hydration inhibitors in drilling fluid on wellbore collapse were analyzed. Research has shown that the hydration and expansion of shale can reduce its elastic modulus and cohesive force, but the effect of hydration and expansion on Poisson’s ratio and internal friction angle shows the opposite pattern. After being immersed in drilling fluid for 12 hours, the elastic modulus of shale decreased from 5.3 GPa to 3.9 GPa, and the cohesion decreased from 4.6 MPa to 3.0 MPa. In addition, wellbore collapse and instability in shale mainly occur in the early stages of drilling operations, while wellbore collapse will significantly slow down in the later stages. The wellbore enlargement rate increased to 40% within the first three hours of drilling operations. Moreover, the addition of hydration inhibitors in drilling fluids will prevent further collapse of the wellbore by inhibiting the invasion of water. When the hydration inhibitor in the drilling fluid was increased from 0 to 45 g/m3, the wellbore enlargement rate decreased from 66.2% to 27.8%. This study can provide theoretical reference for maintaining wellbore stability and drilling safety during shale drilling.

To fully understand the factors influencing hydraulic fracture propagation in deep unconventional gas reservoirs, this study takes a block in China as an example. Firstly, a comprehensive geological mechanics model of the reservoir is constructed. From the perspectives of discrete natural fracture modeling, hydraulic fracture propagation analysis, and hydraulic fracturing numerical modeling, an analysis model of the influencing factors of hydraulic fracture propagation in the reservoir is established. This model is then used to conduct an analysis of the influencing factors, laying the foundation for optimizing fracturing design and improving fracturing effectiveness. The study shows that among factors such as cluster spacing, fluid intensity, natural fracture line density, and horizontal stress difference, cluster spacing has the greatest impact on hydraulic fracture propagation in the reservoir, followed by fluid intensity, while horizontal stress difference has the least impact. Under the condition of gradually increasing cluster spacing, the modified reservoir volume will initially increase and then decrease. As fluid intensity gradually increases, the modified reservoir volume will also increase, but due to economic constraints, fluid intensity should not be excessively high. When the natural fracture line density is low, the rate of increase in modified reservoir volume is relatively fast as it increases. However, when the natural fracture line density is high, the rate of increase in modified reservoir volume slows down as it continues to increase. As the horizontal principal stress difference gradually increases, the modified reservoir volume will gradually decrease.