Natural Gas Industry B最新文献

Annular channeling has seriously troubled deep oil and gas exploitation, and the reduction of hydrostatic pressure of cement slurry in the waiting stage is considered one of the main causes of early annular channeling. However, at present, there is still a lack of sufficient research on and understanding of the relationship between the time-varying law of hydrostatic pressure of cement slurry and the early hydration process in different well sections, especially in high-temperature well sections. Therefore, in this paper, a hydrostatic pressure measurement experiment of cement slurry at low temperature (50–90 °C) and high temperature (120–180 °C) was carried out using a self-developed hydrostatic pressure measurement device of cement slurry. Then, the cement slurry cured at 90 °C for 1–8 h was sampled by the freeze-drying method, and XRD and TG experiments were carried out. The results show that the hydrostatic curves of low and high temperatures both show a trend of rapid increase first, then remain stable, and then decrease rapidly. With an increase in temperature, the time of the stable and falling segments of the hydrostatic curve of the cement slurry gradually decreases. By fitting the rapid pressure drop time points of cement slurry at different temperatures, it can be determined that the rapid pressure drop time and temperature show a functional relationship. The XRD and TG results of different curing times at 90 °C were analyzed. It can be seen that in the early stage of the hydration induction period, the connection between cement particles is not close, and the hydrostatic pressure of the cement slurry column remains stable. As the hydration process enters the acceleration period, the cement particles crosslink with each other through hydration products to form a bridge structure, and the hydrostatic pressure of the cement paste begins to decrease. This shows that the pressure drop time can be controlled by regulating the hydration process to provide theoretical guidance for cement slurry preparation and slurry column design in cementing engineering.

A perpendicular bisector unstructured grid was used for meshing a model with radial wells, and the non-orthogonal correction of the flux calculation was implemented in the Tough+Hydrate software. A numerical simulation model was established based on the geological parameters of hydrate-bearing layers (HBLs) in the Shenhu area of the South China Sea. Gas and water production from the HBL, developed through depressurization of radial wells, was studied, and factors influencing gas production were analyzed. The findings indicate that employing radial wells in both hydrate and mixed layers significantly accelerated gas and water production in the HBL, facilitating rapid depressurization. Faster depressurization, in turn, promoted the dissociation of natural gas hydrate (NGH) and increased gas production. Cumulative gas production using radial wells in double layers increased by 110.03% compared with a horizontal well. In the later stage of depressurization development, NGHs in the mixed layer were almost entirely dissociated, whereas nearly three-quarters of NGHs in the hydrate layer remained undissociated. The combined method of depressurization and thermal stimulation is expected to further promote NGH dissociation and enhance gas production. Analysis of influencing factors revealed that higher gas production was associated with a greater number of laterals and larger lateral length, whereas the layout of the laterals had little effect on performance.

The utilization of hydraulic fracturing for the extraction of natural gas hydrates in maritime environments has been relatively underexplored in the existing literature. This study introduces a novel approach by employing a fully implicit integration method to construct a two-dimensional temperature distribution model of the wellbore. The model considers critical parameters such as fracturing fluid time, initial temperature, and fracturing fluid displacement to forecast the temperature data of the wellbore and its surrounding environments throughout the entire fracturing process. The investigation reveals that the initial temperature of the fracturing liquid and the duration of the fracturing process exert a substantial influence on the wellbore temperature, whereas the impact of fracturing fluid displacement is found to be minimal. Furthermore, a comparative analysis between the results derived from the proposed model and those obtained from traditional steady-state formulas substantiates the accuracy and efficacy of the developed model. This study significantly advances our comprehension of temperature dynamics within wellbores during hydraulic fracturing operations in maritime environments, thereby offering valuable insights for future endeavors in natural gas hydrate extraction.

During the development of shale gas, various issues such as low individual well production, rapid decline, limited reservoir control, and low recovery rates have arisen. Enhancing shale gas reservoir recovery rates has consistently been a focal point and challenge within the industry. Therefore, this paper employs molecular dynamic (MD) simulation methods to study the adsorption and diffusion characteristics of CH₄/CO₂ at different temperatures and mixing ratios. It compares the effects of temperature and CH₄/CO₂ molar ratio changes on the selectivity coefficient, adsorption capacity, and diffusion coefficient of CH₄/CO₂. The paper also plots the displacement interface and the function of CH₄/CO₂ injection/residual amounts over time. Furthermore, it analyzes the adsorption capacity of molecules on the graphene surface, the migration capacity of molecules in the slit, and the displacement process of CH₄ by CO₂ on the nanoscale, revealing the microscopic mechanism of CH₄/CO₂ competitive adsorption and displacement. The research results indicate that the influence of temperature on the selectivity coefficient is not significant, with an average decrease of 3% for every 20 K rise in temperature. Pressure has a more pronounced effect on the selectivity coefficient, with values around 1.4 at low pressures and around 1.2 at high pressures. Elevating the mole fraction of CO₂ in the binary gas mixture results in an increase in the total adsorption amount and an accelerated variation of adsorption amount with pressure. As the CH₄ mole fraction rises, the diffusion coefficient of CH₄ increases, while the diffusion coefficient of CO₂ diminishes with an increasing CO₂ mole fraction. Under identical conditions, CO₂ exhibits a stronger adsorption capacity over CH₄ in shale organic nanopores, resulting in a concave moon-shaped displacement interface in the model. The larger the pre-adsorption pressure of CO₂, the more intense the movement of CO₂ along the graphene surface, and the faster the diffusion speed of CO₂ along the wall. In a displacement pore (the pore space used to provide the displacement location or site) with a diameter of 3 nm, at smaller pressure differentials (≤10 MPa), the residual amount of CH₄ remains relatively stable without substantial alteration. However, at a pressure differential of 20 MPa, the residual amount of CH₄ decreases rapidly, and the displacement efficiency significantly improves.

Casing deformation and frac-hit pose significant challenges to the development of deep shale gas in southern Sichuan Basin. By analyzing the mechanism and main control factors of casing deformation and frac-hit, two kinds of risk assessment methods were defined, and the overall prevention and control concept and practice were formulated. The results show that initial stress, pore pressure, fault development and large scale fracturing in local block are the main factors leading to the deformation. The development of fracture through well group and uncontrolled fracturing fluid volume are the main factors leading to pressure channeling. Based on this, the risk classification technology of casing deformation and frac-hit is established, and the dual-optimal, dual-control concept and technology are formed. In terms of the prevention and control of casing deformation, the formation of small-diameter bridge plug fracturing, large section combined fracturing, glass beads cementing, single-well staggered and platform straddle fracturing mode, dual-dimension controlled and lift fracturing, hyperbolic diagnosis, etc. Frac-hit prevention and control formed pump sequence optimization mode, physical and chemical temporary plugging and other methods. The above technology achieved casing deformation rate decreased from 50.4% to 25.4%, frac-hit rate decreased from 58.6% to 33.9%, and the average well kilometer EUR reached 0.52–0.7 million square meters, an increase of 7.7% compared with the previous research, with remarkable results.

As the demand and import of liquefied natural gas (LNG) increase, large LNG receiving stations are being constructed. LNG leakage can lead to fire or explosion accidents. The simultaneous occurrence of explosions and fires, often inevitable, is more damaging than the effect of a single load. This study utilizes finite element analysis software LS-DYNA and the ALE algorithm to examine the response characteristics and damage effects on large LNG storage tanks under the combined impact of explosion shock waves and high-temperature loads (with the explosion preceding the fire). The findings indicate that post-explosion, the concrete outer tank's compressive strength diminishes as temperatures rise. The dome deflection of the storage tank's external tank surpasses the standard limit at 400 °C and fails at 600 °C. This research identifies the critical failure mode of the concrete storage tank's outer tank under the joint impact of explosion shock waves and fire. It provides a foundation for the anti-explosion design of such storage tanks.

In the pursuit of sustainable oil and gas resource extraction, the innovative integration of carbon capture, utilization, and storage (CCUS) technology has emerged as the most promising approach. During the CCUS process, intricate physicochemical interactions between the injected CO₂, facilitated through various injection strategies (Water Alternative Gas: WAG/Continue Gas Injection: CGI) and the formation fluids and heterogeneous mineral assemblages within the reservoir trigger alterations in mineral structures, consequently impacting permeability and recovery factors, constituting a pivotal aspect. Precisely delineating and quantifying these interactions is paramount for optimizing process design and evaluating reservoir dynamics in the successful implementation of CCUS operations. This study has carried out qualitative and quantitative characterization of mineral heterogeneity, different pore types, and mineral combination characteristics from a low-permeability sandstone reservoir. Additionally, the effect on the physical properties of minerals from different development methods (WAG/CGI) was investigated using numerical simulation for CCUS applications. The results indicate that the saturated CO₂ fluid selectively dissolves the potassium feldspar (orthoclase) in intergranular pores, while the intergranular pores are filled with illite and secondary precipitated clay minerals. It initially dissolves the sensitive mineral (ankerite) in the intergranular pores. The decrease of ankerite and increase of illite result from the prolonged contact period between saturated CO₂ and minerals, which changes the mineral cementation to argillaceous type, thus affecting permeability in the context of CCUS. The spatial impact on reservoir physical properties depends on the spatial heterogeneity of the original sensitive minerals (ankerite, anorthite, illite, etc.) distributed in the study area. In the WAG scheme, the physicochemical interaction between saturated CO₂ and reservoir minerals is more intense than in the CGI scheme for CCUS operations, significantly impacting cumulative production.

Excessive erosion caused by the continuous collision of sand-carrying annular flow with the gas well wellbore can lead to serious production accidents. This study combined the multifrequency response characteristics of sand particle-wall collision with a deep learning algorithm to improve the recognition accuracy of sand particle information in annular flow. The findings showed that sand-wall collision strength was closely related to the velocity, size, and number of sand particles and that the shielding effect generated by the collision behavior between multiple particles had a protective effect on the elbow. In addition, sand-wall collision strength increased with increases in gas velocity and particle size and decreased with an increase in liquid velocity. The shear effect, the secondary flow effect, and the liquid film buffering effect were shown to be key factors affecting the transportation behavior and spatial distribution of sand particles in annular flow. Furthermore, the fast Fourier transform (FFT) and short-time Fourier transform (STFT) analysis results showed that the multifrequency collision response characteristics of sand carrying annular flow were complex and that the main frequency response of sand-wall collision was concentrated in the high frequency range of 50–80 kHz. Moreover, the recognition accuracy results of convolutional neural network (CNN) models for particle size, gas velocity, and liquid velocity were 93.8%, 91.7%, and 91%, respectively, which were significantly higher than the results for the long short-term memory (LSTM) model. The combination of multifrequency collision response and deep learning effectively characterized sand particle feature information in strong gas-liquid turbulence, providing a reference for the accurate monitoring of sand particle information in high-yield water-bearing gas wells.

Geothermal energy is a clean, abundant, and dependable energy source. Because the formation of a geothermal field is often closely linked to the distribution and development of granite, it is crucial to understand the regularity and formation mechanism of granite geothermal resources to advance the field of geothermal energy. Lancang County is located on the southern edge of the Lincang granite, and contains many hot springs. In this paper, we synthesize rock geochemistry, zircon U–Pb chronology, and other methods to interpret the genesis of granites in Lancang County and their geothermal formation patterns. The study area mainly comprises a Middle Triassic S-type granite with high contents of heat-producing elements. Zircon U–Pb dating results show that the intrusion time of the Lancang granite was 239 Ma. The granite is rich in light rare earth elements, depleted in heavy rare earth elements, and characterized by a negative Eu anomaly. The ɛ_Hf values range from −20.3 to 13.6, indicating the presence of mantle material in the source area. Igneous rocks in Lancang County likely formed in the background of an active continental margin associated with the subduction of the Tethys Ocean to the east, which formed an intra-land orogeny. High contents of radioactive thermogenic elements in the granite, fracture development, and additional heat sources from metamorphic rocks combined to generate high-temperature geothermal resources in the study area. The hydrothermal geothermal model of the granite has the following characteristics: a near heat source, large drop, water storage in fractures, simultaneous geothermal influence in deep and shallow layers, and hot spring and geothermal distribution along deep and large faults, etc. The geothermal reservoirs in the study area are classified into four types: internal fissures in granite, granite paleo-weathering crust, tectonic nappe fractures, and sedimentary deposits associated with granite cooling collapse. These types are of great significance to the understanding of the formation of hydrothermal geothermal heat in this granite area.