Gas Water Distribution Research Articles

Analysis of Water Production Factors of Gas Wells in Sulige Gas Field

Abstract The Sulige gas field, characterized by its low porosity and poor permeability, faces challenges in managing the complex gas-water distribution, which has become a growing concern as the field develops. This complexity, coupled with the varied and intricate nature of water production, has impacted the field’s efficiency. To tackle this issue, a study was carried out on water-producing gas wells within the field, examining the production mechanisms, main factors, and distribution patterns. The study found that in the field’s central region, the gas-water ratio in water-producing wells is relatively stable, with some wells yielding over 0.8m3 of water per day. The water sources include formation water, pore water, and water from the wellbore edges and bottom, as well as industrial water usage. Understanding these factors helps mitigate the negative impact of water production on field development and provides guidance for managing similar gas fields effectively.

Invasion Characteristics of Marginal Water under the Control of High-Permeability Zones and Its Influence on the Development of Vertical Heterogeneous Gas Reservoirs

In-depth understanding of the gas–water seepage law caused by different degrees of gas layer perforation and varying gas production rates is key to determining a reasonable development technology policy for vertical heterogeneous edge-water gas reservoirs. Based on core physical data from the entire section of the X2 well, a large-scale high-pressure positive-rhythm profile model that takes into account the influence of “discontinuous interlayer” was innovatively established. The water intrusion process of the gas layer profile under different gas production rates and degrees of gas layer perforation was simulated using an electrical resistivity scanning device. The experimental model has an area of 3000 cm2, with a maximum pressure of 70 MPa and a maximum temperature resistance of 150 °C. It includes 456 evenly distributed fluid saturation test points to accurately monitor the gas–water distribution, addressing the issues of small bearing pressure and insufficient saturation monitoring points found in other large-scale models. The experimental results show that, in heterogeneous reservoirs, the high-permeability zone controls the invasion path of edge water, which is the main reason for the uneven invasion of edge water. For the positive-rhythm profile of the F layer, a higher gas production rate (1000 mL/min) shortens the water-free gas recovery period of the gas well and reduces the recovery rate. Perforating the upper two-thirds of the layer can inhibit edge-water breakthrough, prolong the water-free gas recovery period of the gas well, enable the gas–water interface to advance more uniformly, and enhance the recovery degree. The results of this study greatly enhance our understanding of the water invasion characteristics of positive-rhythm reservoirs under the influence of different gas production rates and varying degrees of gas layer perforation.

Distribution and Main Controlling Factors of Gas and Water in Tight Sandstone Gas Fields: A Case Study of Sudong 41-33 Block in Sulige Gas Field, Ordos Basin, China

Distribution and Main Controlling Factors of Gas and Water in Tight Sandstone Gas Fields: A Case Study of Sudong 41-33 Block in Sulige Gas Field, Ordos Basin, China

Angle-dependent seismic attenuation-based gas-bearing detection of a sandstone river channel reservoir in the western Sichuan Basin

Abstract The shallow river channel sandstone reservoirs of Jurassic in the western Sichuan Basin are rich in natural gas. The gas-bearing sweet-spot has a ‘sausage-like’ distribution feature, with complex gas water distribution. Analyses of seismic data at different angles show that gas-bearing reservoir formation has different seismic attenuation features from the water-bearing formations, and such differences have a certain correlation with gas production. Accordingly, a gas-bearing detection technology based on angle-dependent seismic attenuation feature is proposed. First, the matching-pursuit time-frequency analysis method is used to extract high-resolution time-frequency spectra from seismic data at different incidence angles. Then, the angle-dependent seismic attenuation attribute is estimated using the extracted time-frequency spectra. Finally, the attribute is combined with the inverted impedance for gas-bearing detection. With the advantages of lower uncertainty and being less affected by reservoir porosity, the application results of the developed method have a high coincidence rate with the drilled wells, and the drilling wells deployed based on the detection results have achieved high production.

Study on the Flow Behavior of Gas and Water in Fractured Tight Gas Reservoirs Considering Matrix Imbibition Using the Digital Core Method

Tight gas reservoirs possess unique pore structures and fluid flow mechanisms. Delving into the flow and imbibition mechanisms of water in fractured tight gas reservoirs is crucial for understanding and enhancing the development efficiency of such reservoirs. The flow of water in fractured tight gas reservoirs encompasses the flow within fractures and the imbibition flow within the matrix. However, conventional methods typically separate these two types of flow for study, failing to accurately reflect the true flow characteristics of water. In this study, micro-CT imaging techniques were utilized to evaluate the impact of matrix absorption and to examine water movement in fractured tight gas deposits. Water flooding experiments were conducted on tight sandstone cores with different fracture morphologies. Micro-CT scanning was performed on the cores after water injection and subsequent static conditions, simulating the process of water displacement gas in fractures and the displacement of gas in matrix pores by water through imbibition under reservoir conditions. Changes in gas–water distribution within fractures were observed, and the impact of fracture morphology on water displacement recovery was analyzed. Additionally, the recovery rates of fractures and matrix imbibition at different displacement stages were studied, along with the depth of water infiltration into the matrix along fracture walls. The insights gained from this investigation enhance our comprehension of the dynamics of fluid movement within tight gas deposits, laying a scientific foundation for crafting targeted development plans and boosting operational efficiency in such environments.

Design and investigation of novel gradient flow fields for proton exchange membrane fuel cell

Ensuring sufficient gas supply and high distribution uniformity are crucial issues in the flow field design to improve the performance and durability of proton exchange membrane fuel cell (PEMFC). However, previous studies often ignore the gas-water distribution variations along the flow direction and adopt identical design for the entire flow field, resulting in unsatisfactory performance. To fill in this gap, this paper innovatively proposes two types of gradient flow field (gradient narrowing and gradient droplet) considering the gas-water distribution characteristics. The channel of the gradient narrowing flow field gradually decreases in all directions along the flow direction, and the gradient droplet flow field is composed of staggered droplet blocks, and the distribution density gradually decreases along the flow direction. The Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method is used for the comprehensive evaluation of flow fields. The results demonstrate that the gradient flow field can significantly improve the performance and physical field distribution. The gradient narrowing flow field has the best performance, with 11.39 % improvement in peak power density, 77.96 % increment in average oxygen mass fraction, and 43.11 % improvement in oxygen uniformity compared to parallel flow field. Further, the key geometric parameters sensitivity analysis of gradient narrowing flow field is carried out. This study contributes to understanding the underlying mechanism of mass transfer properties in the novel gradient flow field, and exploring its potential for high-performance flow fields design.

Characterization of Lower Paleozoic Water and Gas Distribution in Yan'an Gas Field, Ordos Basin.

The distribution of gas and water in the tight gas reservoirs is complex. This limits exploration and development compared to conventional resources. Elucidating the characteristics that control fluid distribution is critical to unlocking the tight gas potential. This study combines geologic analysis with production data to reveal the water chemistry, gas-water distribution, and factors controlling zoning in the study area. The results show that (a) extracted water includes formation brines, condensate, and residual drilling fluids; (b) formation water dominates production, and the salinity of Lower Paleozoic brines is as high as 169,689 mg/L; (c) low NaCl and high metamorphic coefficients indicate that the water bodies are disconnected and the hydrocarbons are well-preserved in several gas-water systems; and (d) paleomorphological features, tectonics, and lithologies control the distribution of gas water. Discrete water bodies are widely distributed.

Tight gas charging and accumulation mechanisms and mathematical model

The gas-water distribution and production heterogeneity of tight gas reservoirs have been summarized from experimental and geological observations, but the charging and accumulation mechanisms have not been examined quantitatively by mathematical model. The tight gas charging and accumulation mechanisms were revealed from a combination of physical simulation of nuclear magnetic resonance coupling displacement, numerical simulation considering material and mechanical equilibria, as well as actual geological observation. The results show that gas migrates into tight rocks to preferentially form a gas saturation stabilization zone near the source-reservoir interface. When the gas source is insufficient, gas saturation reduction zone and uncharged zone are formed in sequence from the source-reservoir interface. The better the source rock conditions with more gas expulsion volume and higher overpressure, the thicker the gas saturation stabilization and reduction zones, and the higher the overall gas saturation. When the source rock conditions are limited, the better the tight reservoir conditions with higher porosity and permeability as well as larger pore throat, the thinner the gas saturation stabilization and reduction zones, but the gas saturation is high. The sweet spot of tight gas is developed in the high-quality reservoir near the source rock, which often corresponds to the gas saturation stabilization zone. The numerical simulation results by mathematical model agree well with the physical simulation results by nuclear magnetic resonance coupling displacement, and reasonably explain the gas-water distribution and production pattern of deep reservoirs in the Xujiaweizi fault depression of the Songliao Basin and tight gas reservoirs in the Linxing−Huangfu area of the Ordos Basin.

Saturation Height Modelling for Tight Sandstone Reservoirs with Gas Diffusion Dynamics Taken into Account

Interpreting and predicting the saturation of tight sandstone gas reservoirs are the key task to improve the reservoir development. The role of gas diffusion dynamics is stronger than that of buoyancy during the gas accumulation of tight sandstone reservoirs. In this study, a saturation height model that takes gas diffusion dynamics into account is proposed, which can complement logging saturation interpretation and provide a better practice in saturation prediction. Taking the study of the Sulige tight sandstone gas reservoir in China as an example, the saturation height model compares the controlling factors and uncertainties affecting the saturation distribution, characterizes the complex gas-water distribution, and determines the lower gas charging limits. This study concludes that the configuration between gas diffusion dynamics and reservoir capillary pressure controls the distribution of saturation. The buoyancy effect only serves to improve the saturation at regional uplifts with good petrophysical properties. The different saturation characteristics in the central, western, and eastern parts of the Sulige gas field are precisely caused by the different configurations of source rock quality and reservoir quality. This study provides a key reference for static model and development deployment.

Controls on Gas-Reservoir Formation in the Benxi Formation in the Ganquan–Fuxian Area of the Ordos Basin, China

The Benxi Formation is one of the most important gas-producing layers in the Ganquan–Fuxian area, but the complex gas–water distribution and lack of sandstone have severely constrained natural gas exploration and development in this area. This study analyzed the structure, paleogeomorphology, sedimentary facies, reservoir closures, and gas–water distribution of the Benxi Formation in the study area through drilling, coring, logging, seismic surveying, and experimental testing. The results show that the gas reservoirs in the Benxi Formation are mainly lithologic traps distributed along NW-trending barrier sandstones, with a small portion of updip pinchout closures. The water layers are mainly composed of thin sandstones with a single-layer thickness of less than 2 m, which are tidal-channel or barrier-margin microfacies sandstones. The water saturation in some thick sandstones is related to the activity and destruction of large individual faults. The dry layers are tight sandstones with porosity of less than 3.2%, mainly associated with high amounts of volcaniclastic matrix and lithic fragments, as well as compaction. The charging of the underlying high-quality Ordovician limestone reservoirs by carboniferous source rocks in the Benxi Formation reduces the probability of gas accumulation in Benxi sandstone. Based on the control of sedimentary facies and physical properties on gas accumulation, favorable reservoir distributions were predicted using seismic attributes and gas detection methods, providing the basis for the next phase of natural gas exploration and development in this area.

Driving Forces of Natural Gas Flow and Gas–Water Distribution Patterns in Tight Gas Reservoirs: A Case Study of NX Gas Field in the Offshore Xihu Depression, East China

The driving forces behind gas flow and migration, as well as the associated gas–water distribution patterns in tight gas reservoirs, are not only closely related to the formation mechanisms of “sweet spots”, but also serve as crucial geological foundations for the development of efficient modes and optimal well placement. In this work, three methods, namely, critical gas column height driven by buoyancy, critical pore throat radius driven by buoyancy, and gas–water distribution attitude, were used to quantitatively evaluate the critical conditions for buoyancy and overpressure to get gas flowing in the tight sandstone gas field. In light of the geological background, the driving forces of gas flow/migration and gas–water distribution patterns were comprehensively analyzed. On this basis of the origins of overpressure driving gas flow/migration were identified by using multiple empirical methods, the evolution of overpressure and characteristics of gas–water distribution driven by overpressure were studied by using PetroMod_2014 simulation software. The results show that the four main gas-bearing layers in the NX tight sandstone gas reservoir differ widely in gas flow/migration dynamics and gas–water distribution patterns. Gas accumulation in the H3b layer is influenced by both buoyancy and overpressure. Subsequently, buoyancy leads to the differentiation of gas from water based on density and the formation of edge water. Furthermore, the distribution area of the gas reservoir is determined by the presence of an anticline trap. In contrast, in H3a, H4b and H5a gas layers, buoyancy is not sufficient to overcome the capillary force to make the gas migrate during and after accumulation, and the driving force of gas flow is the overpressure formed by fluid volume expansion during hydrocarbon generation of Pinghu Formation source rocks. Because buoyancy is not the driving force of natural gas flow, H3a, H4b and H5a layers have gas and water in the same layer and produced together, and no boundary and bottom water, where the anticlinal trap does not control the distribution of gas and water, and gas source faults control the boundary of the gas reservoir. These understandings not only significantly expand the gas-bearing target of H3a, H4b and H5a gas layers delineated in the buoyancy driving pattern but also provide an important geological basis for the formulation of an efficient development plan by class and grade for the NX tight sandstone gas field.

Assessment of CO2 storage potential in high water-cut fractured volcanic gas reservoirs—Case study of China’s SN gas field

CO2 storage is an important technique for achieving both carbon peak and carbon neutralization, and depleted gas reservoirs are primary potential candidates for geological CO2 storage. After 15 years of development, the recovery rate of the SN gas field in China has reached 70 % and entered the middle and late stages. Most importantly, it has entered the stage of high water cut, rendering the stabilization of production challenging. As the gas produced in this gas reservoir contains a considerable amount of CO2, high water-bearing wells can be selected for CO2 storage in volcanic depleted gas reservoirs on site. Therefore, in this study, combined with the salinity characteristics of the formation water of the target block, a buried-potential evaluation study on typical wells in volcanic gas reservoirs is conducted, the gas–water distribution characteristics of the gas reservoir after CO2 injection are evaluated, and the CO2 injection timing and volume are optimized. The results show that the different ion content in the formation water leads to two reaction processes: dissolution and precipitation of reservoir minerals. When the CO2 in the formation water is low, the reservoir is dominated by dissolution reaction and the CO2 mineralization buried amount is negative; gradually decreasing with the age of the reservoir. As more CO2 is injected into the formation, a considerable amount of HCO3– is produced. In this context, the formation water is dominated by a precipitation reaction, and the CO2 mineralization buried amount is positive. In 2026, compared with the dissolved buried capacity of 1.0 × 105 m3/d, the injection rate of 2.5 × 105 m3/d will increase by 6.38 × 108 mol. When the injection rate is 1.5 × 105 m3/d, the mineralization buried capacity is the highest (2.02 × 105 mol.). Combining the total amount of CO2 dissolution and mineralization storage, the total amount of storage is the highest (1.38 × 108mol.) when the injection rate is 2.5 × 105 m3/d, indicating that the SN volcanic gas reservoir has significant CO2-storage potential. Guided by the research results of this study, typical wells have been selected to inject CO2 for storage purposes.

The application of basin modeling of oil and gas systems based on the capillary-gravity concept

ANNOTATION Oil and gas reservoirs exhibiting low reservoir properties often have significant deviations in structure of hydrocarbon reservoirs they contain, based on anticlinal theory of oil and gas accumulation. First, these deviations are related to sharp fluctuations found in water-oil and water-gas interfaces and failure to subordinate the shape of deposits to structural factor. When dealing with such objects, geologists often have to assign unreasonable structural deflections, various impermeable seals of tectonic or sedimentary origin whose presence is not always confirmed by seismic and drilling data. The reason for such difficulties is that anticlinal theory does not consider capillary forces counteracting hydrocarbon migration to be key to reservoir formation. Any oil and gas reservoir is a multiphase pore system with countless contacts, both between different fluids and in host pore space. As per molecular physics laws, the major role in oil and gas water distribution in such systems is controlled primarily by capillary properties of the environment such as capillary pressure at water-oil interface, interfacial tension magnitude, pore channel radius and wetting behavior of solid phase. Due to capillary forces, sharp fluctuations at water-oil interfaces and significant shifts of oil and gas reservoirs relative to vaults of anticlinal structures are observed

Gas and water distribution characteristics of water-driven gas process in tight sandstone gas reservoirs: A microscale study by molecular simulation and experiment

Predicting gas and water distribution is an essential step in developing gas reservoirs. This study aims to study the characteristic distribution law of gas and water during waterflooding, which are important in wettability alteration to enhance gas reservoir recovery. Herein, we report a novel method that uses molecular dynamics (MD) associated with a microscopic waterflooding experiment to obtain the characteristic distribution law of gas and water in porous media. We show that this approach may better understand the relationship between gas and water in porous media than conventional technologies. The waterfront in the hydrophilic channel is 13.3 Å more advanced than that in the neutral channel, indicating that the water displacement efficiency in hydrophilic channels exceeds that in neutral channels. Meanwhile, the water flows mainly along the walls of the pores and reduces the diameter of the permeate channel in hydrophilic porous media. While in neutral porous media, the above phenomenon is significantly weakened, and the waterflooding front is relatively consistent. Most importantly, the experimental and simulation results are consistent, and a quantitative evaluation of the gas–water distribution in porous media is given. Additionally, technologically, wettability directly affects the distribution characteristics of fluids in porous media, and changing the wettability characteristics of reservoir rocks is beneficial to delaying the waterflooding front. This approach provides an essential theoretical basis for developing water-driven gas reservoirs.

A new dynamic imbibition model for penny-shaped blind pores in shale gas well

Penny-shaped blind pores are common in shale, these pores with the original gas occurrence, including free gas and adsorbed gas, are seriously affected by a large amount of imbibed fracturing fluid. The competitive gas–water adsorption mechanism and the equations of gas-water phase pressures were analyzed statistically to detail the changes in gas–water distribution during imbibition. Based on the Lucas–Washburn equation, a new dynamic imbibition model is established for penny-shaped blind pores in shale gas reservoirs, which first considers the resistance of desorption of adsorbed gas and free gas and the factors of pore shape and fractal characteristics. The experimental validation, dimensionless-type curve, and common features of the new model regarding water imbibition are analyzed in detail. The results indicated that the proposed model is suitable for accurately predicting the imbibition in blind pores, and the dimensionless-type curve can simplify the calculation process for imbibition predictions. Factor analysis showed that penny-shaped pore width and length are two important factors for imbibition, the smaller width and the longer length, the more imbibition. Meanwhile, the increase of gas-water interfacial tension and displacement pressure is conducive to imbibition, the increase of initial gas pressure and desorption of adsorbed gas is obstructive to imbibition. The research is not only applicable in shale gas reservoir but also useful for geological hydrogen storage, carbon dioxide storage and geothermal development.

A three dimensional visualized physical simulation for natural gas charging in the micro-nano pore system

A micro-nano pore three-dimensional visualized real-time physical simulation of natural gas charging, in-situ pore-scale computation, pore network modelling, and apparent permeability evaluation theory were used to investigate laws of gas and water flow and their distribution, and controlling factors during the gas charging process in low-permeability (tight) sandstone reservoir. By describing features of gas-water flow and distribution and their variations in the micro-nano pore system, it is found that the gas charging in the low permeability (tight) sandstone can be divided into two stages, expansion stage and stable stage. In the expansion stage, the gas flows continuously first into large-sized pores then small-sized pores, and first into centers of the pores then edges of pores; pore-throats greater than 20 μm in radius make up the major pathway for gas charging. With the increase of charging pressure, movable water in the edges of large-sized pores and in the centers of small pores is displaced out successively. Pore-throats of 20–50 μm in radius and pore-throats less than 20 μm in radius dominate the expansion of gas charging channels at different stages of charging in turn, leading to reductions in pore-throat radius, throat length and coordination number of the pathway, which is the main increase stage of gas permeability and gas saturation. Among which, pore-throats 30–50 μm in radius control the increase pattern of gas saturation. In the stable stage, gas charging pathways have expanded to the maximum, so the pathways keep stable in pore-throat radius, throat length, and coordination number, and irreducible water remains in the pore system, the gas phase is in concentrated clusters, while the water phase is in the form of dispersed thin film, and the gas saturation and gas permeability tend stable. Connected pore-throats less than 20 μm in radius control the expansion limit of the charging pathways, the formation of stable gas-water distribution, and the maximum gas saturation. The heterogeneity of connected pore-throats affects the dynamic variations of gas phase charging and gas-water distribution. It can be concluded that the pore-throat configuration and heterogeneity of the micro-nanometer pore system control the dynamic variations of the low-permeability (tight) sandstone gas charging process and gas-water distribution features.

Evaluation of gas-rich “sweet-spot” and controlling factors of gas–water distribution in tight sandstone gas provinces: An example from the Permian He8 Member in Sulige Gas Province, central Ordos Basin, Northern China

The objective optimization of the gas-rich “sweet-spot” is the key to efficient exploration of tight sandstone gas reservoirs. However, research on evaluating the gas-rich “sweet-spot” based on the controlling factors and models of gas–water distribution of tight sandstone is limited. The sand bodies of the Permian He8 Member in Sulige Gas Province of the Ordos Basin are fluvial-delta distributary channels; the gas reservoir porosity dominantly ranges from 6% to 12%, with an average of 8.78%, and exhibits the permeability of (0.1–1) × 10–3 μm2, with a median of 0.38 × 10–3 μm2. The gas reservoirs are tight lithologic lens type with no edge and bottom water, showing a large-area quasi-continuous distribution with horizontal contiguous and vertical multi-layer superposition. Formation water related to the reservoir accumulation process is classified into paleo-formation water, paleo-condensate water, and present-condensate water. The controlling factors of gas production via the source rock and reservoir conditions exhibit distinct stages. The relationships between gas production and the source rock Ro, HGI, reservoir porosity, and permeability are positive, when gas production is <1 × 104 m3/d. However, it can be controlled by a combination of factors when gas production is >1 × 104 m3/d. Formation water production is related to a low HGI, poor physical reservoir properties, large sandstone thickness, excessive fracture development, and gaseous water condensation. Three gas–water distribution models of the gas-rich, moderate gas-rich, and complex gas–water types were established because of the accumulation conditions and gas test results in different areas. The gas-rich type (water-poor gas reservoir) is represented by the Suzhong, Sudong-I and Sudong-III areas, moderately gas-rich type (water-less gas reservoir) is distributed in the Sunan area, and gas–water complex type (water-rich gas reservoir) is mainly distributed in the Suxi-I, Suxi-II, and Sudong-II areas. Based on the analyses of the high weighted parameters of the controlling factors, the values of the gas reservoir comprehensive evaluation index (F) for commercial gas well area, low production gas well area, and gas-containing well area were >31, 26–31, and <26, respectively.

Gas–water distribution pattern of large-scale low and gentle structure gas reservoirs — a case study of the Longwangmiao Formation gas reservoir in MX gas field in Sichuan Basin

Gas–water distribution pattern of large-scale low and gentle structure gas reservoirs — a case study of the Longwangmiao Formation gas reservoir in MX gas field in Sichuan Basin

Research on Test and Logging Data Quality Classification for Gas–Water Identification

Tight sandstone oil and gas reservoirs are widely distributed, rich in resources, with a bright prospect for exploration and development in China. Due to multiple evolutions of the structure and sedimentary system, the gas–water distribution laws are complicated in tight sandstone gas reservoirs in the northern Ordos area. It is difficult to identify gas and water layers in the study area. In addition, in the development and production, various factors, such as the failure of the instrument, the difference in construction parameters (injected sand volume, flowback rate), poor test results, and multi-layer joint testing lead to unreliable gas test results. Then, the inaccurate logging responses will be screened by unreliable gas test results for different types of fluids. It is hard to make high-precision fluid logging identification charts or models. Therefore, this article combines gas logging, well logging, testing and other data to research the test and logging data quality classification. Firstly, we select reliable standard samples through the initial gas test results. Secondly, we analyze the four main factors which affect the inaccuracy of gas test results. Thirdly, according to these factors, the flowback rate and the sand volume are determined as the main parameters. Then, we establish a recognition chart of injected sand volume/gas–water ratio. Finally, we proposed an evaluation method for testing quality classification. It provides a test basis for the subsequent identification of gas and water through the second logging interpretation. It also provides a theoretical basis for the exploration and evaluation of tight oil and gas reservoirs.

Control of differential diagenesis of tight sandstone reservoirs on the gas–water distribution: A case study on the Upper Paleozoic He 8 Member in the northern Tianhuan depression of the Ordos Basin

The sandstone reservoirs in the Upper Paleozoic He 8 Member in the northern Tianhuan depression of the Ordos Basin are vastly different and feature particularly complex gas–water distributions. Scanning electron microscopy, fluorescence, Raman spectroscopy inclusions, relative permeability analysis, and nuclear magnetic resonance were utilized in this study based on core data, identification statistics, and various thin-section microscope measurements. Samples from the Upper Paleozoic He 8 Member in the northern Tianhuan depression were collected to study the characteristics of reservoir heterogeneity and gas–water distribution, which were controlled by differential diagenesis. The results indicate that compaction and dissolution are the two most important factors controlling reservoir heterogeneity. Large differences in diagenesis–accumulation sequences and pore structure characteristics affect reservoir wettability, irreducible water saturation, and gas displacement efficiency, thereby controlling the gas–water distribution. The He 8 Member is a gas reservoir that is densified because of accumulation. Reservoirs can be divided into three types based on the relationship between diagenetic facies and gas–water distribution. Type I is characterized by weak compaction, precipitate or altered kaolinite cementation, strong dissolution of diagenetic facies, and high porosity and permeability. This type is dominated by grain-mold pores and intergranular dissolution pores and produces gas reservoirs with high gas yield. Type II is characterized by medium-strength compaction, altered kaolinite or chlorite cementation, weak dissolution of diagenetic facies, and medium porosity and permeability. This type is dominated by residual intergranular pores, a few residual intergranular pores, and dispersed dissolution pores, producing gas reservoirs with low gas yield. Type III is characterized by medium-strength compaction, altered kaolinite cementation, and medium-strength dissolution of diagenetic facies. This type is dominated by kaolinite intercrystal pores and dispersed dissolution pores, producing gas reservoirs with high water yield.