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Sensitivity analysis of parameters affecting nano-polymer solution for water shutoff in carbonate rocks
Get PDFExcessive water production impacts the economics of petroleum reservoir and often leads to their premature shut-in. Production of high saline water represents a major corrosion for casing, tubing, flow lines, and production facilities. Polymer solution has been used to control water production and to plug in high-temperature reservoirs. Most of these polymer solutions consist of polyacrylamide-based polymer and an organic or inorganic cross linker. Polyethylene mine has been used as an organic cross-linked for polyacrylamide. Literature reported that polyethylene mine can also form ringing gels with polyacrylamide copolymers in addition to polyacrylamide concentration. In this study, nano-chemical solutions has been prepared and studied in detail for their efficacy at reservoir condition. The compositions of the nano-chemicals mainly consisted of polyacrylamide mixed with nano particles, cement, coated-clay and polyethylene mine as cross-linker. The aim of using nano particles and coated-clay was to control gel performance and strength under the reservoir condition. Moreover, the effect of nano-chemical composition at higher temperature have been studied extensively on the gelation properties, elastic modulus, viscosity, and swelling ratio. Results showed that the elastic modulus and viscosity improve significantly with the increasing nano particle concentration. Coated-clay can control the gelation time as clay swallows and absorbs more formation water in the target zone, when its thin coated film breaks down, lesser water production can be predicted.Cited as: Soka, S., Sidiq, H. Sensitivity analysis of parameters affecting nano-polymer solution for water shutoff in carbonate rocks. Advances in Geo-Energy Research, 2022, 6(3): 230-240. https://doi.org/10.46690/ager.2022.03.0
The influence of adsorption layer thickness and pore geometry on gas production from tight compressible shales
Get PDFIn tight shales, gas is stored in both free and adsorbed form. A one-dimensional model is derived for shale gas production by pressure depletion where the adsorbed layer thickness is of similar magnitude as the pore radius and can affect flow performance. The adsorbed layer thickness is a function of pressure. Different pore geometries are assumed varying continuously between spherical pores to more fracture shaped pores. The shale is assumed compressible and its porosity and pore radius reduce with pressure depletion. The effective pore radius (pore radius minus adsorption layer thickness) controls intrinsic and apparent permeability. The impact of the adsorption layer, compressibility and geometry are investigated. A given adsorbed layer thickness fills more of the pores when they are more spherical and concentrates more of the volumetric flow to the effective pore boundaries giving lower permeability for a given effective radius. Increasing the adsorbed thickness increases the adsorbed fraction initial gas in place. A high volume fraction adsorbed gas reduces apparent permeability and delays production. Pressure depletion causes both pore radius and adsorbed layer to be reduced. The change in adsorbed layer thickness is low at high pressure and greater at low pressure, while pore radius changes more linearly and more with higher compressibility. The free gas saturation and slip increases with pressure depletion for low compressible cases, but if matrix compression dominates there can be a net reduced permeability. Recovery was linear with the square root of time for all cases. Adsorbed gas is less effectively produced by pressure depletion than free gas and higher adsorbed content by more spherical pores or higher layer thickness reduces end recovery. Higher compressibility reduces permeability and delays recovery but increases end recovery. Higher compressibility reduces permeability and delays recovery but increases end recovery.Cited as: Abolghasemi, E., Andersen, P.Ø. The influence of adsorption layer thickness and pore geometry on gas production from tight compressible shales. Advances in Geo-Energy Research, 2022, 6(1): 4-22. https://doi.org/10.46690/ager.2022.01.0
Criteria and favorable distribution area prediction of Paleogene effective sandstone reservoirs in the Lufeng Sag, Pearl River Mouth Basin
Get PDFAs the focus of conventional oil and gas exploration is changing from shallow to deep layers, the identification of deep effective reservoirs is crucial to exploration and development. In this paper, based on the geological anatomy of oil and gas reservoirs, a new discriminatory criterion and evaluation method for effective reservoirs is proposed in combination with the analysis of reservoir formation dynamics mechanism. The results show that the hydrocarbon properties of the reservoir vary with the ratio of the capillary force between the sandstone reservoir and its surrounding rock. The effective reservoir is discriminated and the reservoir quality is evaluated based on the capillary force and depth of the surrounding media and the sandstone reservoir for adjacent plates. When the capillary force ratio is greater than 0.6, fewer effective reservoirs are developed. The effective reservoir is determined by the capillary force ratio of the sandstone reservoir and the surrounding rock medium to mechanically explain the geological phenomenon that low-porosity reservoirs can also accumulate hydrocarbons. Our findings have significant guiding value for Paleogene oil and gas exploration in the Zhu I depression of Pearl River Mouth Basin.Cited as: Yu, S., Wang, C., Chen, D., Guo, B., Cai, Z., Xu, Z. Criteria and favorable distribution area prediction of Paleogene effective sandstone reservoirs in the Lufeng Sag, Pearl River Mouth Basin. Advances in Geo-Energy Research, 2022, 6(5): 388-401. https://doi.org/10.46690/ager.2022.05.0
Liquid phase blockage in micro-nano capillary pores of tight condensate reservoirs
Get PDFThe development of tight condensate gas reservoirs faces complex formation damage mechanisms, seepage characteristics and hydrocarbon phase changes, which are common challenges for both tight gas reservoirs and condensate gas reservoirs. In the near-well area, the liquid phase blockage problem due to water phase retention formed by capillary spontaneous imbibition of invasive water and oil phase accumulation due to retrograde condensation precipitation has become a key obstacle to the efficient development of tight condensate gas reservoirs. Experiments were conducted to evaluate the damage of liquid phase blockage under different conditions near the wellbore area. The results show that when the liquid phase saturation in the near-wellbore area increased to 80.12%, the relative permeability of the gas phase decreased to 0. It is concluded that the mixed wettability of formation rocks, ultra-low water saturation, abundant hydrophilic clay minerals and high capillary resistance of micro-nano pores are the main causes for the easy adsorption and retention of liquid phase. Reduced pressure transmission capacity and irreversible formation damage induced by liquid-phase blockage are the two major controlling factors for the low liquid phase flowback rate. It is suggested that developing a flowback system based on the formation physical properties differentiation to control water phase invasion, and changing wettability or injecting thermochemical fluid to control condensate blocking are feasible methods to relieve liquid phase blockage damage in tight condensate reservoirs.Cited as: Wang, Y., Kang, Y., Wang, D., You, L., Chen, M., Yan, X. Liquid phase blockage in micro-nano capillary pores of tight condensate reservoirs. Capillarity, 2022, 5(1): 12-22. https://doi.org/10.46690/capi.2022.01.0
Hydrocarbon dynamic field division and its relevance to oil and gas exploration for Paleogene reservoir in Lufeng Depression
Get PDFSignificant breakthroughs have been achieved in the exploration of Paleogene reservoirs in the Lufeng Depression. However, as drilling depth is becoming greater, the discovered oil and gas reservoirs show signs of transition from conventional to unconventional accumulations, and the identification of conventional and unconventional reservoir boundaries is of particular significance. Herein, the hydrocarbon dynamic field boundaries in the Lufeng Depression are comprehensively identified by the geological drilling result method, the sandstone pore throat radius critical value discrimination method and the dry layer drilling rate variation method; then, the hydrocarbon dynamic field is divided and the characteristics and differences of hydrocarbon accumulations in each hydrocarbon dynamic field are compared. The results show that the buoyancy-driven hydrocarbon accumulation depth in the Lufeng Depression is between 3,500-4,000 m, and the hydrocarbon accumulation depth limit is about 5,800 m. The focus of research on Paleogene oil and gas exploration in the Lufeng Depression should be placed on conventional oil and gas reservoirs in the free dynamic field and tight oil reservoirs in the reformed dynamic field. As for the Enping Formation and Upper Wenchang Formation, efforts should concentrate on conventional oil and gas reservoir exploration, and the tight reservoir of Lower Wenchang Formation should be explored in the high fracture density area in C-4 and C-8 well blocks and the west of C-8 well block of the Lufeng 13 sag. The research results of this paper are of great value in further increasing oil and gas production and the explorarion of reservoirs in the Lufeng Depression.Cited as: Ma, K., Pang, H., Zhang, L., Huang, S., Huo, X., Chen, J. Hydrocarbon dynamic field division and its relevance to oil and gas exploration for Paleogene reservoir in Lufeng Depression. Advances in Geo-Energy Research, 2022, 6(5): 415-425. https://doi.org/10.46690/ager.2022.05.0
Characterization of marine shale in Western Hubei Province based on unmanned aerial vehicle oblique photographic data
Get PDFThe marine shale in the Sinian Doushantuo Formation of Qinglinkou outcrop section is well developed, but the current characterization methods for outcrops are unsatisfactory. In this paper, the data of outcrop in the field study area were collected by Unmanned Aerial Vehicle, then processed and interpreted by oblique photography technology combined with manual investigation. Subsequently, we established a quantitative geological knowledge database of the shale formations and carried out the typical section of anatomy analysis. The results showed that the high-precision image information captured by unmanned aerial vehicle oblique photography technology can be well coupled with a three-dimensional coordinate system. The three-dimensional digital model was used to characterize the lithologic assemblage, thickness and distribution characteristics of the target reservoir. Based on this digital model, we established the three-dimensional lithology and the total organic carbon models of the outcrop area. The spatial distribution characteristics of interbedding between marine dolomite and shale in the outcrop area were displayed, and the distribution of total organic carbon was revealed under lithological constraints. The models are beneficial for the analysis and prediction of the lithology and total organic carbon, which is of great significance to the understanding of shale gas sweet spots.Cited as: Yin, S., Feng, K., Nie, X., Chen, Q., Liu, Y., Wang, P. Characterization of marine shale in Western Hubei Province based on unmanned aerial vehicle oblique photographic data. Advances in Geo-Energy Research, 2022, 6(3): 252-263. https://doi.org/10.46690/ager.2022.03.0
Advances in multiscale rock physics for unconventional reservoirs
Get PDFThe multiscale rock physics of unconventional reservoirs have drawn increasing attention in recent years, which involves several essential issues, including measuring method, transport property, physics model, characteristic scale, and their application. These issues vastly affect science and engineering regarding the exploration and development of unconventional reservoirs. To encourage communication on the advances of research on the rock physics of unconventional reservoirs, a conference on Multiscale Rock Physics for Unconventional Reservoirs was jointly organized by the journals Energies and Advances in Geo-Energy Research. Due to the limitations of movement caused by COVID-19, 21 experts introduced their work online, and the conference featured the latest multiscale theories, experimental methods and numerical simulations on unconventional reservoirs.Cited as: Cai, J., Zhao, L., Zhang, F., Wei, W. Advances in multiscale rock physics for unconventional reservoirs. Advances in Geo-Energy Research, 2022, 6(4): 271-275. https://doi.org/10.46690/ager.2022.04.0
Wormholes effect in carbonate acid enhanced oil recovery methods
Get PDFAcid enhanced oil recovery has been a focus of interest in the oil industry due to its significant results on improved recovery, especially in carbonate reservoirs. However, in carbonate reservoirs, highly conductive pathways called “wormholes” are created when acidic fluids are injected into carbonate rocks. Wormholes could jeopardize the enhanced oil recovery outcome and sweep efficiency leaving a substantial volume of oil in the reservoir unswept. This phenomenon has not been investigated yet. The main objective of this study is to identify the impact of these wormholes on the overall oil recovery during enhanced oil recovery practices. This was achieved by injecting acidic fluid into Indiana limestone at various injection rates to control the creation of wormholes. The injection rates were selected based on a proposed dimensionless phase space that predicts the wormholes development and dissolution phase. Our results show that wormholes have a significant impact on the enhanced oil recovery performance resulting in a decrease in the overall oil recovery by 9.6% for portions of the reservoir that experience wormholing. In real field applications, it is recommended to avoid creating wormholes over large portions of the reservoir affected by acid injection as it may jeopardize the field development outcome leaving an unspecified amount of oil in virgin regions in the reservoir which results in additional operational complications. Wormholes are only beneficial near the wellbore for wellbore cleanup and matrix treatment purposes thus providing easier access to the reservoir. However, care needs to be taken to constrain wormhole formation to skin factor reduction and avoid far-reaching wormholes in the reservoir.Cited as: Alarji, H., Clark, S., Regenauer-Lieb, K. Wormholes effect in carbonate acid enhanced oil recovery methods. Advances in Geo-Energy Research, 2022, 6(6): 492-501. https://doi.org/10.46690/ager.2022.06.0
Comparative study on the thermal performance and economic efficiency of vertical and horizontal ground heat exchangers
Get PDFThe ground-coupled heat pump is a shallow geothermal exploitation method taking soil as the thermal energy source. The ground heat exchanger is an important component of this system, which includes vertical or horizontal configurations. However, to the best of our knowledge, few studies exist involving the comparison of thermal performances and installation costs of two heat exchanger types considering the influence of ground climate, which makes the selection of heat exchanger configuration challenging for a specific field application. Hence, a 3-dimensional numerical model considering the variations of atmospheric conditions and soil water content is constructed in this paper. Based on this model, the thermal performances and economical efficiencies of vertical and horizontal ground heat exchangers are compared. The results indicate that the thermal performance difference between the two heat exchangers is greater in winter than in summer. The thermal performance is hardly influenced by the injection mass flow rate, while it is considerably affected by the length of heat exchanger. The thermal power rises linearly with the increase in heat exchanger length, and the increment of the vertical ground heat exchanger is higher. In addition, when the heat exchanger length is shorter than 40 m, the installation cost and thereby the total cost of the horizontal ground heat exchanger is considerably higher. With regard to both the thermal performance and economic efficiency, a vertical ground heat exchanger is only recommended when installing a single shallow ground heat exchanger.Document Type: Original articleCited as: Cui, Q., Shi, Y., Zhang, Y., Wu, R., Jiao, Y. Comparative study on the thermal performance and economic efficiency of vertical and horizontal ground heat exchangers. Advances in Geo-Energy Research, 2023, 7(1): 7-19. https://doi.org/10.46690/ager.2023.01.0
Improving recovery efficiency by CO2 injection at late stage of steam assisted gravity drainage
Get PDFThe high recovery performance of steam-assisted gravity drainage (SAGD) makes it a popular option for heavy oil resources. Currently, most of the heavy oil reservoirs developed by SAGD in China are in the late development phase, with high energy consumption due to reduced thermal efficiency. The use of SAGD wind-down processes involving CO2 in combination with steam for heavy oil recovery is considered as a viable alternative to limit energy consumption, and also reduce the amount of greenhouse gas emissions by leaving CO2 behind in the reservoir. Study reveals that the dissolution and demulsification of CO2 steam chamber temperature reaches 200 ◦C, the amount of solid phase deposition induced in crude oil can reduce the viscosity of emulsified heavy oil by more than 50%. When the by CO2 extraction is only 0.016 kg/m3 , the rock wettability changes from lipophilic to hydrophilic, and the higher the reservoir temperature, the stronger the hydrophilicity is, which reduces the adhesion power of the oil phase and facilitates the stripping of crude oil from the rock surface. Numerical simulation studies have been carried out utilizing STARS to obtain energy efficient utilization and improved steam chamber characteristics. Heat loss from SAGD baseline is 1.77 times that with CO2 injection process, but the recovery factor is only 2.48% higher. At the initial stage with CO2 injection, the steam chamber continues its lateral expanding, which increases the recovery factor at the initial stage of CO2 injection by about 6%. One year after CO2 injection, gas channeling results in lower recovery than traditional SAGD process, and 38.4% of the injected CO2 is stored in the reservoir from this study.Cited as: Gong, H., Yu, C., Jiang, Q., Su, N., Zhao, X., Fan, Z. Improving recovery efficiency by CO2 injection at late stage of steam assisted gravity drainage. Advances in Geo-Energy Research, 2022, 6(4): 276-285. https://doi.org/10.46690/ager.2022.04.0