Gas Zone Research Articles

Optimal design of the field hydrate production test in the offshore India: Insights from the vertically heterogeneous hydrate reservoir model

Recently, the hydrate-bearing sand reservoirs were founded with high saturation in the offshore India by the National Gas Hydrate Program Expedition 02 (NGHP-02). Based on the detailed geological data at the NGHP-02-16 site, a more realistic reservoir model is constructed to analyze the unique multiphase flow and hydrate phase change behaviors from the geologically descriptive hydrate reservoirs. The main goals of this work are to optimize the adjustable production parameters and to predict the long-term gas production performance for guiding the upcoming field hydrate production test in India. The results indicate that gas production rates increase, but water production rates decrease slowly with time from the heterogeneous hydrate-reservoir. This is completely different from the previous prediction of multiphase flow behavior based on homogeneous hydrate-reservoir models. A non-uniform hydrate dissociation front is formed in the hydrate-reservoir due to the reservoir heterogeneity promote the horizontal dissociation of solid-hydrate within the high permeability sand layers. The maximum distance of free gas zone expands to outside more than 500 m from the production well. This indicates that the field fault system should be carefully concerned during the long-term production. Sensitivity analysis results suggest that the complete perforation in the hydrate-bearing layer and the underlying water saturated layer is beneficial for improving the hydrate production performance. Over the 5 years depressurization, a total of 2.08 × 107 ST m3 methane gas can be produced using the recommended well placement. The average gas-to-water ratio and energy ratio reach 10.22 ST m3 CH4/m3 H2O and 30.14, respectively, showing a high gas production potential from this hydrate site.

Mathematical modeling of foamy-oil flow in a cyclic solvent injection process

Foamy-oil flow is one of the main mechanisms for cold heavy oil production with sand (CHOPS) and cyclic solvent injection (CSI) processes. The flow pattern of foamy oil was observed in previous experimental studies under reasonable reservoir conditions. This study aims to investigate the foamy-oil flow mechanisms through theoretical modeling. A mathematical model is developed, which couples a solvent concentration field and a pressure field through flow velocity and oil viscosity, in which a pseudo-chemical reaction is used to describe the release of gas. The model is numerically solved by the Newton−Raphson iterative method. Results show that, firstly, during the pressure drawdown process, propane concentration decreases and oil viscosity increases with solvent exsolution in the transition zone, which restricts the bubbles coalescence and conduces to the formation of foamy oil. Secondly, the existence of bubbles leads to the buildup of local pressure gradient and causes the spatial difference of flow velocity. Moreover, when the threshold velocity is reached, the bubbles coalesce rapidly to form free gas, pushing the oil in the foamy region forward to the gas zone. Finally, the total waves of foamy-oil flow are generally 2 to 4, depending on the initial solvent concentration, oil viscosity, and pressure depletion rate. Higher initial solvent concentration, faster pressure depletion, and lighter original heavy oil lead to the easier induction of foamy-oil flow.

A detailed general model of the gasification zone of a dual fluidised bed gasifier

A detailed general model of the gasification zone of a dual fluidised bed gasifier

Impact of Gas Saturation and Gas Column Height at the Base of the Gas Hydrate Stability Zone on Fracturing and Seepage at Vestnesa Ridge, West-Svalbard Margin

The Vestnesa Ridge, located off the west Svalbard margin, is a >60 km long ridge consisting of fine-grained sediments that host a deep-marine gas hydrate and associated seepage system. Geological and geophysical observations indicate the predominance of vertical fluid expulsion through fractures with pockmarks expressed on the seafloor along the entire ridge. However, despite the apparent evidence for an extended free gas zone (FGZ) below the base of the gas hydrate stability zone (BGHSZ), present-day seafloor seepage has been confirmed only on the eastern half of the sedimentary ridge. In this study, we combine the relationships between aqueous phase pressure, capillary pressure, sediment clay fraction, porosity, and total stress to simulate how much gas is required to open preexisting fractures from the BGHSZ towards the seafloor. Data from four specific sites with different lithology and pressure regime along the ridge are used to constrain the simulations. Results demonstrate that fracturing is favored from the FGZ (with gas saturations < 0.1 and gas column heights < 15 m) towards the seafloor. Neglecting the capillary pressure overpredicts the size of the gas column by up to 10 times, leading to erroneous maximum gas vent volume predictions and associated ocean biosphere consequences. Further parametric analyses indicate that variations in the regional stress regime have the potential to modify the fracture criterion, thus driving the differences in venting across the ridge. Our results are in line with independent geophysical observations and petroleum system modeling in the study area, adding confidence to the proposed approach and highlighting the importance of the capillary pressure influence on gas pressure.

New development of sensitivity improvement for compensated neutron porosity tool in gas-filled boreholes

Porosity is one of the most important indicators used for hydrocarbon reservoir evaluation and extraction. However, obtain accurate formation porosity measurements in gas-filled boreholes can be challenging, this is because gas cannot slow down neutrons as effectively as water due to its lower hydrogen index, which results in measurement sensitivity reduction and consequently impacts the obtained porosity. One way to address this issue is loading water into the borehole which is commonly referred to as water loading. However, this process significantly increases operational time and cost, as well as shielding perforated gas zones. Therefore, a new strategy is proposed to improve the sensitivity of porosity measurement in gas or air-filled boreholes without the need for water loading. The key to this strategy is to incorporate a sleeve design outside the tool to enhance its performance in gas-filled intervals. The sleeve is composed of a downhole applicable material whose neutron slowing down ability is close to water. The optimized deployment orientation of the sleeve could then be determined through simulation. In this work, three potential sleeve materials are identified and compared based on an existing neutron porosity tool. The impacts of different tool-sleeve-borehole orientations are analyzed to determine the most effective design strategy. A series of test pit experiments is conducted to validate the feasibility of the design.

Управление аэрологическими рисками в подготовительных выработках угольных шахт

Objective. The purpose of the research is to assess the indicators of aerological risk in the development workings of highly gas-rich coal mines. Introduction. The results of a retrospective analysis are presented, substantiating that the vast majority of explosions of dust-methane-air mixtures occur in development workings, and 63.8% of their gassing with methane to explosive concentrations is associated with ventilation disorders. Methodology. The assessment of aerological risk consists in the calculation of some indicators that reflect the measure of danger, in which an accident may occur, caused by the excess of the values of the mine atmosphere parameters in comparison with the normative ones. Indicators of the main hazards and vulnerability of ventilation schemes and methods make up the general structure of risk in development workings. Results. The methodological bases for assessing and forecasting the aerological risk of accidents in development workings are presented. A formula for calculating the predictive indicator of aerological risk is given. In accordance with the methodology, it is possible to quantify the reduction in the level of aerological risk when managing outgassing with the help of degassing. Discussion. Calculations have shown that the schemes and methods of ventilation of dead-end workings, in which there is a large degree of influence of the activity of mixing gases in the bottomhole zone and a small degree of influence of the exhaust gas zone on ventilation, are the most effective, with a normal level of safety. The values of the predicted upper-air risk indicator reach unity for the schemes and methods of ventilation of dead-end workings with a low degree of gas mixing activity in the bottomhole zone and a high degree of influence of the exhaust gas zone on ventilation, which indicates an extremely high level of explosiveness. Conclusions. Application of the developed methodology allows not only forecasting aerological risks during design, but also justification of aerological safety.

Evidence of coal conversion in the Majuba underground coal gasification pilot plant, South Africa

Underground coal gasification (UCG) is a coal conversion method that permits coal resources to be exploited in situ using high-temperature conversion reactions. An understanding of the chemical, mineralogical, and petrographic properties of the coal, and resultant unburned carbon, degasified coal, and ash (minerals) in the UCG gasification zone, is fundamental to determining conversion rates, gas composition, and environmental and groundwater risk assessments. This study aims to provide a mineralogical and petrographic characterization of UCG residues obtained from the Eskom Majuba UCG pilot plant site in South Africa. Samples were selected from a verification borehole (VH3) drilled at the site following the pilot trial. The Permian-age Karoo Basin Majuba Gus Seam coal is medium rank C bituminous, inertinite-rich, with variable ash content. All the coal samples extracted from the borehole show evidence of heating and conversion. The volatile matter content is very low, and the mean random vitrinite reflectance values are above 5 (%RoVmr). It is possible to use vitrinite reflectance data to estimate the probable temperatures achieved in the UCG georeactor. The UCG samples in this study were exposed to maximum temperatures of around 1300°C. There is a very slight temperature gradient through the seam, indicative of fairly even heat distribution and release of volatile gases. Cracks within the degasified coals were filled with molten glassy material. Most of the iron sulfide mineralization is the degasified coal samples was transformed to pyrrhotite. The gasified samples show lower levels of sulfur as compared to unheated coal from this seam.

A Numerical Model for Determining Deep Methane Flux Linked to the Free Gas Zone: Application to the Ocean Drilling Program Site 995 and Implications for Regional Deep Methane Flux at the Blake Ridge

The lack of the quantification of deep dissolved methane flux prevents us from accurately understanding hydrate accumulation and distribution at a given geologic setting where vertically upward methane advection dominates the hydrate system. The upward deep methane flux was usually applied as an assumed value in many previous studies. Considering the deep methane flux changes the methane concentration in the pore water and further affects the phase transfer between the gas and aqueous phases depending on the in situ methane concentration, we link gas bubbles distribution to deep dissolved methane flux. Here, we constructed a numerical model to quantify the dissolved methane flux from depth based on the parameters related to gas bubble distribution, including the residual gas saturation in sediments and the free gas zone (FGZ) thickness. We then applied our model to ODP Site 995 at the Blake Ridge where methane was sourced from deep layers. Our model results predict an upward deep methane flux of 0.0231 mol/m2/a and the occurrence of another gas interval in deeper sediments, which are consistent with seismic data. We further explored the influence of upward methane flux on hydrate accumulation and found that the thin hydrate occurrence zone at nearby Site 994 likely resulted from a small deep methane flux. Combined with the previous conclusion of high deep methane flux at Site 997, we showed that along the Blake Ridge drilling transect the estimated deep methane fluxes decrease with increasing distance from the crest of the ridge. This approach for quantifying deep methane flux is complementary to the current hydrate accumulation model and provides new insights into the regional methane flux estimation at the Blake Ridge.

Thermodynamic modeling for confined fluids in nanopores using an external potential-advanced equation of state

Quantitatively understanding thermodynamic properties of confined fluids in nanoporous media is of great significance to the development of shale gas. Due to the complex intermolecular forces in the nanopore, it is difficult to accurately predict the thermodynamic properties of fluid molecules. Focusing on the fluid-fluid and fluid-wall molecules interactions in shale reservoir system, the thermodynamic model of fluid molecules in pores is constructed, and a modified equation of state is proposed by systematically coupling the original Soave-Redlich-Kwong equation of state with Tjatjopoulos-Feke-Mann potential model in this work. The advanced EoS could facilitate a good prediction on thermodynamic properties of confined fluids without any introduction of new empirical parameters. For verification, fluid density as the important thermodynamic property was targeted and pure methane at a wide pressure range was employed to represent the fluid. The results indicated that the calculated densities accord well with the reported ones in the free gas zone. The deviation of discrete density ranges from 0.239% to 1.7329%. The fluid density distribution in the nanopores is found to be nonuniform, exhibiting a greater value near the wall than that in the pore center, which would be ascribed to the more dominant fluid wall molecule interaction. For example, the local density is 16.90 kg/m3 in the pore center, while it increases to 26.67 kg/m3 in the region which is 0.76 nm to the wall at 350 K, 3 MPa, and 5 nm (radius). Moreover, effects of other critical factors on fluid density distribution were also conducted, and it was indicated that higher pressure, lower temperature, and smaller pore size could be favorable for the occurrence of confined fluid. In general, the novel EoS could provide a quantitative and simple method in predicting the thermodynamic properties of confined fluids relating to applications of shale gas storage and exploitation.

Gas prediction using an improved seismic dispersion attribute inversion for tight sandstone gas reservoirs in the Ordos Basin, China

Predicting gas saturation is critical for identifying gas zones in tight sandstones, but poroelastic behaviours of tight sandstones with low porosity and permeability lead to complex relationships between gas saturation and elastic attributes. Thus, gas prediction based on conventional seismic methods tends to be a challenging task. However, the frequency-dependence of elastic properties associated with fluid flow in tight sandstones allows the utilisation of seismic dispersion attributes for gas prediction. This study proposes a new inversion method to compute the bulk-modulus-related dispersion attribute DK for improved gas prediction by using the sensitivity of the bulk modulus to fluids in tight sandstones. Rock physical modelling and synthetic tests indicate that the proposed DK exhibits increased sensitivity to gas saturation compared to the conventional P-wave velocity dispersion attribute DP and the commonly utilised VP/VS ratio. Real data applications demonstrate that DK represents a preferable gas identification factor for the tight sandstone gas reservoir in the Ordos Basin. Results indicate that DK shows improved apparent anomalies to gas zones and better correspondence with the actual production status of drilled wells than DP and the VP/VS ratio. A combined factor, CF, is further proposed to improve the accuracy and robustness of gas prediction by considering the sensitivity of DK while simultaneously incorporating the VP/VS ratio as an essential constraint. A close correlation between the proposed CF and gas saturation measured in boreholes justifies the applicability of the CF for the reliable identification of gas-bearing tight sandstones. Gas zones identified by the CF provide essential information for gas exploration in the region of interest. The method proposed in this study extends the existing seismic dispersion inversion for improved gas prediction. The methodology to obtain the gas identification factor can inspire the development of other practical fluid indicators.

Effect of fuel flexibility on combustion performance of a micro-mixing gas turbine combustor at different fuel temperatures

An H-class gas turbine combustor prototype that employs the micro-mixing combustion technology is first proposed in the current research. It consists of 60 interior jet-in-crossflow micro-mixing nozzles with a distributed arrangement. To analyze the fuel flexibility, a blend of 50% H2 and 50% CO by volume and the pure H2 are considered for the micro-mixing combustor prototype in terms of the design and alternative fuels, respectively. Secondly, this research discusses the fuel temperature effects on the rated and off-design combustion performance for both fuels, because the fuel temperature is an important factor for the power generation efficiency in the gas turbine combined cycles. The results indicate that at the rated fuel temperature of 473 K and off-design ones of 423, 523 and 573 K, the micro-mixing combustor prototype has a great fuel flexibility, in which NO emission is lower than 15 μL/L at 15% O2, outlet temperature distribution factor is lower than 15%, combustion efficiency is higher than 99%, and total pressure recovery factor is higher than 95% for both fuels. Through the trends of combustion performance in different radial planes, it can be found that the high temperature zone of flue gas produced by H2 is longer than H2/CO (50%/50%), and far away the nozzles. Thus, the H2-fired micro-mixing combustor prototype needs a longer axial liner length than H2/CO (50%/50%), in order to realize the enhanced temperature distribution uniformity and combustion efficiency. Eventually, an optimal relationship between the axial liner length and fuel hole diameter is proposed for both fuels based on the trade-offs around the whole combustion performance from the perspective of engineering applications.

Critical Zone Structure by Elastic Full Waveform Inversion of Seismic Refractions in a Sandstone Catchment, Central Pennsylvania, USA

AbstractSeismic imaging provides key information for revealing structures within Earth's critical zone (CZ) and quantifying subsurface fluid properties. The P‐wave velocity (Vp) models estimated by seismic refraction tomography or acoustic full waveform inversion (FWI) are useful to delineate the thicknesses of weathered bedrock but ambiguously map fluid properties in CZ. Considering the complementary sensitivity of S‐wave to subsurface fluid saturation, we explore advanced elastic full waveform inversion (EFWI) to estimate both Vp and S‐wave velocity (Vs) models simultaneously. Several strategies are proposed for robust EFWI implementation of noisy single (vertical) component refraction data: (a) we window seismic data to preserve early arrivals mainly including P‐wave, converted waves, and S‐wave refractions; (b) we use a correlative misfit rather than the classic L2 misfit to alleviate the interference of unreliable data amplitudes; and (c) we perform inversion using a multiscale frequency strategy with the iterative constraint with the rule of Vp/Vs > 1. We validate that the EFWI approach reliably reconstructs Vp and Vs models using synthetic data. Then, we apply our EFWI approach to seismic refraction data acquired at the Garner Run site of the Susquehanna Shale Hills Critical Zone Observatory. The inverted Vp and Vs models indicate three distinguished layers and with significant lateral and depth heterogeneities (e.g., low Vp and Vs zones). Joint analyses of Vp, Vs, and Vp/Vs with rock‐physics knowledge reveal potential gas or water gathering zones.

Identification of Favorable Zones of Gas Accumulation via Fault Distribution and Sedimentary Facies: Insights From Hangjinqi Area, Northern Ordos Basin

The Hangjinqi area was explored for natural gas around 40 years ago, but the efficient consideration in this area was started around a decade ago for pure gas exploration. Many wells have been drilled, yet the Hangjinqi area remains an exploration area, and the potential zones are still unclear. The Lower Shihezi Formation is a proven reservoir in the northern Ordos Basin. This study focuses on the second and third members of the Lower Shihezi Formation to understand the controlling factors of faults and sedimentary facies distribution, aimed to identify the favorable zones of gas accumulation within the Hangjinqi area. The research is conducted on a regional level by incorporating the 3D seismic grid of about 2500 km2, 62 well logs, and several cores using seismic stratigraphy, geological modeling, seismic attribute analysis, and well logging for the delineation of gas accumulation zones. The integrated results of structural maps, thickness maps, sand-ratio maps, and root mean square map showed that the northwestern region was uplifted compared to the southern part. The natural gas accumulated in southern zones was migrated through Porjianghaizi fault toward the northern region. Well J45 from the north zone and J77 from the south zone were chosen to compare the favorable zones of pure gas accumulation, proving that J45 lies in the pure gas zone compared to J77. Based on the faults and sedimentary facies distribution research, we suggest that the favorable zones of gas accumulation lie toward the northern region within the Hangjinqi area.

Natural gas content of the “Five-meter” coal seam of the Neryungrinskoye field

The article examines, analyzes and consolidates the results of research (direct and indirect research methods) of the gas content of the “Five-meter” seam of the Neryungrinsky coal deposit, which is slated for underground mining. The article also presents the criteria that determine the representativeness of the tested samples by the direct method, which allow the introduction of indirect methods for studying the gas content of the “Pyatimetrovy” formation of the Neryungri field without losing the reliability of the results. As a result of the analysis of the factual material and the geological situation at the field, as well as taking into account the data on the current state of open pit mining at the field, the following were identified: the main factors influencing the degree and nature of the gas content of the Pyatimetrovy layer of the Neryungrinskoye field; composition of gases, the inflow of which is expected to enter the mine atmosphere during mining operations to extract coal from the “Five-meter” seam by the underground method. The main results of the research presented in the article are: the identification of two main gas zones of the “Five-meter” formation with the construction of a gas zoning diagram along the depth of the formation; determination of the presence of gas traps at the field with low production rate of free gas, which are determined by the presence of permafrost in the field; establishing the influence of open pit mining at the deposit on the activation of the natural degassing process of the coal seam and its host rocks at the present stage. The quantitative indicators of the methane content of the coal seam in the field have been established, it has been noted that natural gases in the host rocks are identical to those in the reservoir.

Enrichment control factors and exploration potential of lacustrine shale oil and gas: A case study of Jurassic in the Fuling area of the Sichuan Basin

Well Taiye 1 in the Fuling area of the eastern Sichuan Basin has obtained a high-yield industrial gas flow (7.5 × 104 m3/d gas and 9.8 m3/d oil) from the Middle Jurassic Lianggaoshan Formation, presenting a good test production effects, which means the realization of a major breakthrough in the exploration of Jurassic lacustrine shale oil and gas in the Sichuan Basin. In order to further determine the exploration potential of lacustrine shale oil and gas in this area and realize the large-scale efficient development and utilization of lacustrine shale oil and gas, this paper analyzes the geological conditions for the accumulation of lacustrine shale oil and gas in this area by using the drilling data of 10 key wells, such as wells Taiye 1 and Fuye 10. Then, the main factors controlling the enrichment of lacustrine shale oil and gas are discussed, and the exploration potential and favorable target zones of Jurassic lacustrine shale oil and gas in the Fuling area are defined. And the following research results are obtained. First, the quality Jurassic semi-deep lake shale in the Fuling area is characterized by high organic matter abundance, high porosity and high gas content, and it is the geological base of shale oil and gas enrichment. Second, the developed large wide and gentle syncline, good preservation condition and higher pressure coefficient (generally >1.2) are the key to the enrichment and high yield of shale oil and gas. Third, the developed microfractures in lacustrine shale are conducive to the enrichment and later fracturing of shale oil and gas. In conclusion, the Lianggaoshan Formation lacustrine shale in the Fuling area is widely distributed with moderate burial depth, developed microfractures and moderate thermal evolution, and its shale gas resource extent and shale oil resource extent are 1 922 × 108 m3 and 2800 × 104 t, respectively, indicating greater potential of shale oil and gas exploration, so shale oil and gas is the important field of oil and gas reserves and production increase in this area in the following stage.

Research progress of tunnel air-tight concrete

With the quick development of transportation network construction, the tunnel construction has been an important part. During the tunnel construction process, especially in the gas zone, gas leaking has been a common problem. For avoiding gas leakage, it is necessary to enhance the air-tightness of the tunnel concrete, air-tight concrete is a kind of concrete with excellent air tightness performance. In this paper, we introduced the research progress of tunnel air-tight concrete, including the effect of mix ratio, composition on the air-tight performance of tunnel concrete and corresponding characterization methods.

Heat and mass transfer mechanism of micro-combustion system with dual-fuel at high environmental load

• Heat release mechanism in micro-combustion process with dual-fuel is investigated. • Focusing on the temperature variation of the field at high environmental load. • The depressurization process results in an adiabatic expansion phenomenon. • The out-of-phase blowout effect always exists. • The temperature structure shows large differences with initial states. Heat release and mass transfer characteristics in micro power unit with dual-fuel at high environmental load are mainly investigated in this paper. Energy conversion equations are solved in both phases separated by a regressing gas-solid interface. The igniter jet is assumed as a cross flow and then added to the gas governing equations in the form of source terms. Analyses have focused on variations in temperature, heat release rate per volume and species concentration. Results show that the forced-convection heat transfer in the gas flame zone is performed under the effect of the cross flow. Meanwhile, the rapid depressurization process of the micro system results in an adiabatic expansion phenomenon of the combustion-gas near the solid surface. However, the sandwich propellant can always keep burning due to the continuous addition of energy source from the igniter combustion-gas of high temperature. The out-of-phase blowout effect, that is, the gas zones with strong heat release always keep away from the solid surface, also appears in the whole process. Significantly, when the initial pressure or the average flow velocity of igniter jet is lower than 20 MPa or 40 m/s, the temperature distribution in the flowfield is greatly affected by the initial state.

Sensitivity analysis of injection parameters in steam assisted gravity drainage under geological uncertainty

Steam-assisted gravity drainage (SAGD) is a challenging enhanced oil recovery technique that requires proper parameterization in terms of well geometry and steam injection parameters as these parameters are highly dependent on the reservoir geology and fluid characteristics (e.g., net pay variation, water saturation). Injection rate and pressure, temperature, steam quality, lean zone, gas zone, water saturation, and wellbore hydraulics are among the most important engineering parameters of SAGD. This work focuses in the sensitivity analysis under geological uncertainty of some operational parameters, such as: injection rate, temperature, steam quality and pressure. To reach this objective we build a realistic reservoir model with multiple geological settings and descriptions. Moreover, two complementary approaches were studied: i) a deterministic sensitivity analysis relying on a factorial design matrix and ii) a stochastic analysis using particle swarm optimization. There are several key geological uncertainties in SAGD, such as net pay variation, inclined heterolithic stratification (IHS) presence, high water saturation in reservoirs, bottom water issues, and gas cap problems. This work focuses on the role of porosity and permeability in oil production, as these impact these geological properties. To reach this objective, two specific groups of ten different porosity and permeability pairs of geostatistical realizations were generated using Direct Sequence Simulation and Co-simulation. Group 1 used the same variogram model for 10 random seeds; and Group 2 used a combination of values that adopted a simultaneous and a random variation, which were assigned to the seed and to the variogram. We opted by a reservoir model that mimics an anticlinal reservoir, as it proved to be a determining factor for the low levels of Net Present Value (NPV) when compared to other geological scenarios. Within the four most commonly studied parameters in SAGD projects, the association of deterministic versus stochastic multi-objective analysis allowed to accurately validate injection rate as the most relevant parameter. Regarding the geological uncertainties, Group 1 showed that for a certain porosity distribution and permeability orientation, the random origin of these distribution maps eventually attributed a higher NPV uncertain. On the other hand, in Group 2, the simultaneous spatial and seed variation provided less uncertainty associated to NPV. • Sensitivity analysis under geological uncertainty of SAGD operational parameters. • Impact of small-scale variability of petrophysical properties in SAGD performance. • Deeper understanding of relevant injection parameters that influence the NPV and CSOR. • Comparison between deterministic statistical analysis and stochastic optimization.

Gas channels and chimneys prediction using artificial neural networks and multi-seismic attributes, offshore West Nile Delta, Egypt

Machine learning techniques combined with multi-seismic attributes and well logs datasets have been successfully used in reducing the risk of drilling operations and petroleum exploration by providing precise petrophysical and seismic information extracted from the hydrocarbon reservoir rocks. For this purpose, Artificial Neural Networks (ANNs) work as a multi-channel processing system with a high degree of interconnection to classify various faces and predict the reservoir properties through the seismic profile by involving multi-seismic attributes and optionally well logs to the inputs. The main aim of this study is to use both supervised and unsupervised neural networks for the first time in the West Delta Deep Marine (WDDM) concession to identify the spatial dimensions of the gas-bearing channels and the detection of gas chimneys across the seismic profiles. We use back-error propagation algorithms of the Multilayer Perceptron (MLP) and self-organizing Unsupervised Vector Quantizer (UVQ) as supervised and unsupervised neural network methods, respectively, to detect the gas zones and channels, and to classify the gas chimneys and non-gas chimneys zones, as well as classification of the seismic reflections and lithologies. The output acquires a detailed analysis of the distribution pattern of gas channels and accurate information to image the gas chimneys. In the current study, the approach adopted is beneficial to image the gas chimneys and channels in different basins in any region of the world with similar geological settings. • Artificial Intelligence (AI) identifies the spatial dimensions of the gas-bearing channels. • Use both Multi-Layer Perceptron (MLP) and self-organizing Unsupervised Vector Quantizer (UVQ) to detect the gas zones and channels, classify the gas chimneys and non-gas chimneys zones. • The role of ANNs techniques combined with multi-seismic attributes and well logs in hydrocarbon exploration.

Characteristics of heterogeneous diagenesis and modification to physical properties of Upper Paleozoic tight gas reservoir in eastern Ordos Basin

To correctly evaluate reservoir quality and determine promising tight gas zones, the characteristics of heterogeneous diagenesis and modifications to physical properties in the Upper Paleozoic tight gas reservoir in the eastern Ordos Basin (UPTGREOB) were assessed by comprehensively analyzing lithology, petrophysics, and organic geochemistry data. It was found that the types of sandstones in UPTGREOB mainly include (feldspathic) detritus sandstones and detritus feldspathic sandstone in low–ultralow porosity and permeability, with complex pore structure. Sandstone pores can be divided into two types: primary (primary intergranular and residual primary intergranular pores), secondary (intercrystalline, dissolved intragranular, dissolved intergranular, and dissolved cementing pores and microfractures). The main types of diagenesis are compaction, cementation, dissolution, and metasomatic alteration. Shiqianfeng Formation and Upper Shihezi Formation belong to period B of the syndiagenesis stage and period A1 and A2 of the mesodiagenesis stage; Lower Shihezi Formation and Shanxi Formation are entirely in the mesodiagenesis stage; Taiyuan Formation can be regarded to be in periods A2 and B of the mesodiagenesis stage and period A of the telodiagenesis stage. The original porosity of UPTGREOB was approximately 34%. Compaction was the primary destructive diagenesis rather than cementation, while dissolution was found to be the primary constructive diagenesis. The heterogeneous diagenesis played different roles in the UPTGREOB: in syndiagenesis B, the UPTGREOB began to densify under the compaction and early cementation; in mesodiagenesis A, dissolution and metasomatic alteration produced massive secondary dissolved pores and intercrystalline pores, improving the porosity and permeability; in mesodiagenesis B, dissolved pores were filled by new cements, resulting in decreased porosity and permeability; in telodiagenesis A, intensified compaction and cementation made the UPTGREOB retain extra low porosity and permeability. In general, the reservoirs of Shiqianfeng Formation and Upper/Lower Shihezi Formation in the mesodiagenesis stage A have preferable physical properties for tight gas accumulation.