Gas Reservoir Rocks Research Articles

Influence of asphaltenes on wettability of gas and oil saturated reservoir rock

The wettability of terrigenous and carbonate rock cores of oil and gas condensate fields extracted with n-hexane and chloroform by asphaltenes was studied. The obtained values of core wettability with asphaltenes show their contribution to the change of wettability of different rocks.

Development of a new physical modeling method to investigate the effect of porosity on the parameters of intact rock failure criteria

Porosity is a critical textural parameter in the complex nature of rock and while it has the highest impact on the strength of intact rock, in the case of oil and gas reservoir rocks, it defines the capacity and permeability of the reservoir. A constant value for triaxial strength factor (mi) of rock failure criterion has been given for each type of sedimentary rocks such as sandstone and the effect of porosity on the mi has not been well defined. Rock is not a homogenous material as with varying the porosity, the other inherent variables also control the strength and the mechanical behavior. Rock porosity varies in a wide range in sedimentary rocks such as sandstone. In this study, the effect of porosity on the parameters of failure criteria (mi) for rock-like materials made from cemented grains is investigated. For sample preparation, a mixture of cement-sand-water was compacted with variable water content to obtain specimens having a wide range of porosities using the same grain size of filler material. Two types of grains including sand and silica filler material were used for the experimental program. Sixteen sets of artificial specimens having porosities from 9.00% to 34.09% have been prepared for two filler materials of sand and silica, while other factors affecting the strength have been kept constant. The triaxial strength test results of these specimens show that the triaxial strength factor (mi) of Hoek et al. failure criterion, internal friction angle (ϕ), and cohesive strength (C) significantly decrease with increasing the porosity. The best-fit curves follow power function with high coefficients of regression.

A Method of Differentiating the Early-Time and Late-Time Behavior in Pressure-Pulse Decay Permeametry

The pressure-pulse decay is a preferred technique for determining permeability of unconventional gas reservoir rocks. The pressure-pulse decay often shows quite different characteristics during the early time and the later time. Most approaches for estimating the permeability proposed in the literature are required to use the later-time pressure-pulse decay measurements. However, the later-time data are often selected subjectively, lacking a universal criterion. In this paper, a method of differentiating the early-time and late-time behavior for pressure-pulse decay test is proposed. The analytical results show that the critical time (dimensionless time) of early-/late-time decay characteristics mainly depends on the volume ratios, and it increases first and then decreases with the volume ratios. The critical time for cases with same chamber sizes is much less than that for cases with unequal chamber sizes. Applicability of the proposed methods is examined using a numerical simulator, TOUGH+REALGASBRINE. The numerical results show that the pressure gradient along the sample varies nonlinearly at the early time and becomes a constant at the late time. Then, the proposed method is applied to real data for permeability estimation. It is found that the early-time behavior is negligible as the volume ratio takes on small values. As the volume ratios increase, the deviation becomes significant and considerable permeability errors will be produced if these early-time data are used.

Oil and Gas in Poland: future prospecting and critical points

Shale gas revolution in Poland is over. But several years of shale gas investigations gave a methodic for prospecting and exploitation of various types of unconventional reservoirs. Tight gas reservoir rocks show 10 to 100 times greater permeability than shale reservoir rocks. It is the base to profitable exploitation these reservoirs. The paper relieved and ranked the polish sedimentary basins in context of possibilities of discovery unconventional and low permeable conventional reservoirs. The Miocene sediments of The Carpathian Foredeep, the polish part of the Rotliegend basin, the Carpathians and the Upper Silesian Coal Basin were taken into considerations. Advantages and critical points was discussed.

Experimental and numerical simulation of water adsorption and diffusion in shale gas reservoir rocks

Despite the success of deep horizontal drilling and hydraulic fracturing in yielding large production increases from unconventional shale gas reservoirs, uncertainties associated with basic transport processes require understanding in order to improve efficiency and minimize environmental impacts. The hydraulic fracturing process introduces large volumes of water into shale gas reservoirs, most of which remains unrecoverable and interferes with gas production. In this study, the water adsorption and diffusion measurements of the Longmaxi Formation shale were conducted at 30℃ and 50℃for relative humidities from 11.1% to 97.0%. Based on the experiment, a computational model based on the Maxwell-Stefan diffusion equation was constructed to analyze water adsorption and diffusion in shale rocks, and the Guggenheim-Anderson-de Boer (GAB) isotherm for gas adsorption was included in the model. The results show that water adsorption isotherms of shales belong to type II curve, including the monolayer, multilayer adsorption and capillary condensation, and the GAB model can be used to describe the water adsorption process in shale rocks. With the increasing of relative pressure, the water adsorption of shale increases, and the organic carbon content and temperature strengthen the water adsorption in shale. The capillary pressure can reach the order of several hundreds of MPa after the hydraulic fracturing process, and it results in a large amount of fracturing fluid retained in shale gas reservoirs. Furthermore, the simulations of water adsorption and diffusion in shale rocks is less than the experimental value, which further indicates that capillary condensation occurs in shale rocks. Cited as : Shen, W., Li, X., Cihan, A., Lu, X., Liu, X. Experimental and numerical simulation of water adsorption and diffusion in shale gas reservoir rocks. Advances in Geo-Energy Research, 2019, 3(2): 165-174, doi: 10.26804/ager.2019.02.06

Geomechanical study of gas reservoir rock using vertical seismic profile and petrophysical data (continental shelf in southern Iran)

ABSTRACTGeomechanics is a science dealing with the study of the behaviour of rocks affected by stress. It has various applications in utilisation from oil and gas reservoirs including of the wellbore stability analysis and determination of safe mud window. The main aim of this paper is geomechanical study of Kangan–Dalan reservoir in South Pars gas field in Persian Gulf in south Iran. Seismic waves are affected by physical properties of rocks when passing underground formations; thus, the velocity of these waves is a desired parameter for estimation of geomechanical properties. The velocity of compressional and shear waves has been determined with processing seismic data resulting from vertical seismic profile. In this paper, after calculation of elastic modules of reservoir rock, the imposed stress field was determined and these concepts were used for engineering calculations such as safe mud window, wellbore stability analysis and sand production potential. For well drilling in Kangan-Dalan reservoir, the minimum and maximum mud weights were proposed in average as 1.093 and 2.011 gr/cc and average critical mud weight as 2.48 gr/cc such that if the weight of mud increases, the tensile fractures will be created on the formation and complete loss of mud will happen.

Mathematical modeling of the acoustic and elastic anisotropy of the shale reservoir rocks of the Dnipro-Donetsk depression

The purpose of the work is to analyze the parameters of elastic and acoustic anisotropy in the study of a multicomponent reservoir rock model, which is represented by shale. Research theory To solve this problem, the methods of conditional moment functions using the Mori-Tanaka calculation scheme, as well as the ordinary least squares were used. The technique of effective elastic invariables mathematical modelling of unconventional shale reservoir rocks has been developed. Justification of the mathematical model Eight varieties of mathematical models that characterize the mineral composition, the structure of the void space and elastic properties that are characteristic for shale reservoir rocks of the Dnipro-Donetsk depression in Ukraine were substantiated and developed. The models are based on previous publications by the authors and the results of petrographic studies at the Institute of Geology. Results The authors for the first time carried out an analysis of elastic constant rock models, acoustic tensor components, linearity and shale parameters, isolines stereo projections of index surfaces of nine elastic anisotropy parameters, as well as Thomsen parameters. Acoustic data can be used to trace the change in the structure of the reservoir rock void space, the concentration of rock-forming minerals in the rock. Fracturing has a greater effect on rock structure than granular voids and mineral structure. The orientation of inclusions has the greatest influence on the coefficient of acoustic anisotropy, anisotropy coefficients in rocks, where the voids are oriented in the plane perpendicular to the borehole axis have the largest values (more than 20%). When calculating the Thomsen parameters, the parameters of elastic anisotropy were obtained. They characterize not only the mineral composition of the rocks but also the qualitative structure of the void space, the orientation of minerals and voids in the rocks. Thomsen parameters correlate with acoustic anisotropy parameters for shale reservoir models. The parameters of acoustic and elastic anisotropy are indicators in the studies of similar-type rocks with different types of mineral inclusions and the structure of the void space. The mathematical modelling of elastic and acoustic parameters which characterizes their anisotropy and was carried out by the authors is an important step in substantiating mathematical models of shale reservoir rocks. Such models can be used in the interpretation of geophysical data (seismic surveys and well logging) to make corrections for elastic anisotropy in prospecting and exploration of oil, gas and water saturated unconventional shale reservoir rocks of complex structure, and also to compile a database of mathematical models of reservoir rocks in the given region.

Study of Rock Mechanic Property and Mineralogy Relationship of the Huai Hin Lat Formation, Sap Phlu Basin, Northeastern Thailand: Implications for Understanding of Shale Gas Reservoir Rock

Thailand is lacked of gas that more information of probable (P2) and possible (P3) reserve data including shale gas can be acceptable to prove (P1) reserve data for new gas field. This research had implicated for understanding of unconventional reservoir rock by rock mechanical, micro-CT, and geochemistry analysis of the Huai Hin Lat Formation. The rock mechanical analysis is composed of average young’s modulus, Poisson’s ratio, and compressive strength of 1933.79 MPa, 0.1472, and 52.56 MPa. The average porosity of 6.89% consists of 5.41% and 1.48% of closed and open porosities. The average mineralogical results consist mainly of 57.60% and 42.40% of brittle and ductile minerals indicating more elasticity except Bed 6. The Bed 6 is significantly higher quartz (15%) and brittle minerals (64%) indicating to easier fracture are, therefore, lower compressive strength (25.93 MPa), young’s modulus (1729.10 MPa) and Poisson’s ratio (0.0705). The Beds 3B is slightly higher clay containing slightly higher closed porosity (5.46%) but the Bed 14 is slightly higher brittle mineral indicating to slightly higher open porosity.

Characterizations of full-scale pore size distribution, porosity and permeability of coals: A novel methodology by nuclear magnetic resonance and fractal analysis theory

Nuclear magnetic resonance (NMR) has been widely used to evaluate the pore size distribution (PSD) properties of coals. However, the NMR signal itself only provides a relative distribution of pore size. To calculate an absolute pore size distribution from the NMR data, the T2 cutoff value needs to be known. Meanwhile, the T2 cutoff value is an indicator to divide the irreducible fluid and movable fluid in porous rock and a key factor for permeability prediction. Conventionally, the T2 cutoff value is obtained by centrifugal experiments, the process of which is complicated and time consuming, and some T2 cutoff value prediction models are not suitable for coals with complex pore structures. Hence, a new method is needed for T2 cutoff value prediction. In this study, we performed scanning electron microscopy (SEM), low-temperature nitrogen adsorption/desorption (LTNA) and NMR experiments on 12 coal samples. The results of SEM and LTNA reveal the complex pore structures of the coals. According to the results from centrifugal experiments, the T2 cutoff value is in the range from 0.5–2.8 ms for subbituminous coals, whereas it is 15–32 ms for anthracite coals. We present a fractal theory based method for T2 cutoff value prediction. Using the estimated T2 cutoff values, we calculated the movable porosities, PSD and permeability for the selected coals. The results show that the proposed permeability model provides significantly better permeability estimation than classic (Coates and SDR) models. These methods are applicable not only for coals, but also for other unconventional gas reservoir rocks such as gas shales.

Projekt badawczy: ”Projektowanie, wpływ na środowisko i skuteczność działania energetyzowanych cieczy do szczelinowania skał zbiornikowych ropy i gazu Europy Środkowej” (ENFLUID) – założenia, przebieg i rezultaty

Projekt badawczy: ”Projektowanie, wpływ na środowisko i skuteczność działania energetyzowanych cieczy do szczelinowania skał zbiornikowych ropy i gazu Europy Środkowej” (ENFLUID) – założenia, przebieg i rezultaty

Assessing low-maturity organic matter in shales using Raman spectroscopy: Effects of sample preparation and operating procedure

Laser Raman spectroscopy is used to assess the thermal maturity of organic matter in sedimentary rocks, particularly organic-rich mudstones. However, discrepancies exist between quantified Raman spectral parameters and maturity values obtained by vitrinite reflectance. This has prevented the adoption of a standard protocol for the determination of thermal maturity of organic matter (OM) by Raman spectroscopy. We have examined the factors influencing the Raman spectra obtained from low-maturity OM in potential shale gas reservoir rocks. The inconsistencies in Raman results obtained are due to three main factors that are critically evaluated: (1) different operational procedures, including experiment setup and spectral processing methods; (2) different methods of sample preparation; (3) the analysis of diverse types of OM. These factors are scrutinized to determine the sources of inconsistency and potential bias in Raman results, and guidance is offered on the development of robust and reproducible analytical protocols. We present two new Raman parameters for un-deconvolved spectra named the DA1/GA ratio (area ratio of 1100–1400 cm−1/1550–1650 cm−1) and SSA (scaled spectrum area: sum of total area between 1100 and 1700 cm−1) that offer potential maturity proxies. An automated spreadsheet procedure is presented that processes raw Raman spectra and calculates several of the most commonly used Raman parameters, including the two new variables.

Development of a new rock drillability index for oil and gas reservoir rocks using punch penetration test

Punch penetration test has shown a good relationship with the rate of penetration (ROP) of tunnel boring machine (TBM) into hard rock. In addition, various indices have been determined from the analysis of the force-penetration curve of the penetration test to present rock drillability, boreability, and brittleness. Therefore, in the present paper, punch penetration test will be used to determine rock drillability index (RDI). In this research, 9 samples were taken from the same formation in two wells drilled at southwestern Iran. Considering the limitations in taking more samples, and also to enhance reliability of the results, each of the samples was divided into smaller specimens, so as to conduct multiple tests at each sampling point. Evaluation of the force-penetration curves of samples indicated that most samples of well 1 have little changes of forces early in the test, but they increase as the test proceeds. Because the samples from the Well 1 were taken from shallow depths, The change in the slope of the curve determined on the basis of the samples taken from Well 1 can be explained by the pores existing in these samples. Different indices were extracted from the analysis of the force-penetration curve of each specimen, including first peak slope index (BI1), maximum peak slope index (BI2), area under the curve (BI3), and RDI. Initial examination of relationships between each of indices and the measured ROP follow an either exponential or power-law model. Evaluation of these models between each of these indices and actual ROP indicated that, an exponential curve gives the best fit to the obtained values. A comparison between estimated ROPs from the fitted relationships against measured values showed that the estimated ROP using the proposed index is highly accurate and reliable and can present a good measure of the reservoir rock drillability.

Geological and geophysical analyses of the different reasons for DHI failure case in the Nile Delta Pliocene section

The shallow clastic section in the Nile Delta is characterized by mild velocity variations. The relationship between the expected velocity reduction in the gas reservoir rocks and the encompassing shale is responsible for acoustic impedance contrast, predictable to a particular AVO-class. In class-3AVO, the bright spot is a result of great reduction in velocity increase due to differences between high-velocity encompassing shale and relatively low-velocity reservoir sand. The class-3AVO characterizes a strong seismic amplitude appearance in the full stack section and with similar characteristic view of AVO analysis and interpretation. In addition to the strong amplitude, there are different DHI features related to the gas occurrence. These DHI features are analyzed to achieve and deliver a successful exploratory well. The DHI analysis of one of the unsuccessful cases using recent 3-D seismic data clarifies the importance of the workflow that works for exploring types of anomalies in the Nile Delta. The anomaly is drilled mainly based on an explicit high-amplitude anomaly with local flat spot, but without taking into consideration the extent of DHI characteristics, inherent to gas occurrence in the Nile Delta. Authors investigate all the features related to this unproven case in the form of a postmortem and compare it with proven existing discoveries, to know the possible reason of unsuccessful DHI anomalies in the Nile Delta.

Совершенствование метода оценки проницаемости горных пород-коллекторов природных резервуаров нефти и газа

Совершенствование метода оценки проницаемости горных пород-коллекторов природных резервуаров нефти и газа

СУЧАСНІ ПІДХОДИ ДО ВИЗНАЧЕННЯ ПРОНИКНОСТІ ПОРІД-КОЛЕКТОРІВ ЗА ДАНИМИ ГЕОФІЗИЧНИХ ДОСЛІДЖЕНЬ

Permeability of rock is its physical property that describes its ability to conduct fluids under the pressure gradient. This paper presents short description and analysis of methods for determination of permeability of oil and gas reservoirs. Permeability is a function of different parameters that leads to difficulties during its estimation. Investigations of the void space structure of rocks, their anisotropy etc.were carried out in order to take into account all factors that have an influence on the permeability. Reservoir conditions could also be modeled for that purpose. Methods for determination of permeability of rocks can be divided into three groups: methods based on the laboratory studies of rocks; methods based on the well logging data; and methods based on the correlations between different parameters of rocks. The first two groups include methods for steady and unsteady fluid flow. Methods for the unsteady flow are usually more precise and rapid, thus prospects of extension of methods for permeability determination are mostly connected with them. Each of the presented methods to determine permeability is characterized by some pros and cons. The most appropriate method for the specific experiment is always chosen according to conditions and requirements and expected results. Further author's investigations will be related to the creation of petrophysical models of permeability of oil and gas reservoir rocks, including reservoirs of complex structure.

Analyzing a suitable elastic geomechanical model for Vaca Muerta Formation

Accurate geomechanical evaluation of oil and gas reservoir rocks is important to provide design parameters for drilling, completion and predict production rates. In particular, shale reservoir rocks are geologically complex and heterogeneous. Wells need to be hydraulically fractured for stimulation and, in complex tectonic environments, it is to consider that rock fabric and in situ stress, strongly influence fracture propagation geometry.This article presents a combined wellbore-laboratory characterization of the geomechanical properties of a well in El Trapial/Curamched Field, over the Vaca Muerta Formation, located in the Neuquén Basin in Argentina. The study shows the results of triaxial tests with acoustic measurements in rock plugs from outcrops and field cores, and corresponding dynamic to static correlations considering various elastic models. The models, with increasing complexity, include the Isotropic Elastic Model (IEM), the Anisotropic Elastic Model (AEM) and the Detailed Anisotropic Elastic Model (DAEM).Each model shows advantages over the others. An IEM offers a quick overview, being easy to run without much detailed data for heterogeneous and anisotropic rocks. The DAEM requires significant amounts of data, time and a multidisciplinary team to arrive to a detailed model. Finally, an AEM suits well to an anisotropic and realistic rock without the need of massive amounts of data.

Experimental investigation of Sinian shale rock under triaxial stress monitored by ultrasonic transmission and acoustic emission

To investigate the acoustic and mechanical properties of shale gas reservoir rocks, fracture experiments under triaxial compression were conducted using Sinian shale samples collected from the Sichuan Basin and cored along an angle of ∼15° with respect to bedding orientation. Ultrasonic transmission (UT) and Acoustic emission (AE) were used to monitor the response of anisotropic wave velocity and fracture behavior to elevated stress. X-ray CT (computed tomography) scan was used to explore the heterogeneous structure and geometric property of the fracture zone that ultimately developed in the sample. The evolution of microstructure such as closure of pores, development of microcracks and formation of macro fractures at elevated stress is likely responsible for the observed responses of elastic wave velocity and AE activity. During the hydrostatic compression stage, the closure of cracks and pores leads to a little bit of increase of velocity and a small number of AE events. As the mean effective stress further increases, there is no significant change in the microstructure of shale sample derived from the non-response of velocity to elevated stress. During the dynamic fracture stage, the generation of macro-fracture along the bedding plane accounts for the decrease of velocity as well as the rapid increase of AE activity. Our results indicate that the Sinian shale of the Sichuan Basin is characterized by weak anisotropy and strong heterogeneity in core scales. The intrinsic anisotropy keeps almost unchanged to the elevated stress, while significant increase in velocity anisotropy is induced by shear fracture. Moreover, the fracture experiments show that the shale sample performs a purely brittle fracture behavior, which is beneficial for the hydraulic fracturing stimulation of shale gas reservoirs. Both AE hypocenters and X-ray CT scan image show that the deformation and fracture process correlates strongly with the bedding structure in the sample.

Prestack amplitude versus angle inversion for Young's modulus and Poisson's ratio based on the exact Zoeppritz equations

ABSTRACTElastic parameters such as Young's modulus, Poisson's ratio, and density are very important characteristic parameters that are required to properly characterise shale gas reservoir rock brittleness, evaluate gas characteristics of reservoirs, and directly interpret lithology and oil‐bearing properties. Therefore, it is significant to obtain accurate information of these elastic parameters. Conventionally, they are indirectly calculated by the rock physics method or estimated by approximate formula inversion. The cumulative errors caused by the indirect calculation and low calculation accuracy of the approximate Zoeppritz equations make accurate estimation of Young's modulus, Poisson's ratio, and density difficult in the conventional method. In this paper, based on the assumption of isotropy, we perform several substitutions to convert the Zoeppritz equations from the classical form to a new form containing the chosen elastic constants of Young's modulus, Poisson's ratio, and density. The inversion objective function is then constructed by utilising Bayesian theory. Meanwhile, the Cauchy distribution is introduced as a priori information. We then combine the idea of generalised linear inversion with an iterative reweighed least squares algorithm in order to solve the problem. Finally, we obtain the iterative updating formula of the three elastic parameters and achieve the direct inversion of these elastic parameters based on the exact Zoeppritz equations. Both synthetic and field data examples show that the new method is not only able to obtain the two elastic parameters of Young's modulus and Poisson's ratio stably and reasonably from prestack seismic data but also able to provide an accurate estimation of density information, which demonstrates the feasibility and effectiveness of the proposed method. The proposed method offers an efficient seismic method to identify a “sweet spot” within a shale gas reservoir.

Rare earth element characteristics of the carboniferous Huanglong Formation dolomites in eastern Sichuan Basin, southwest China: Implications for origins of dolomitizing and diagenetic fluids

Marine dolostones of Carboniferous Huanglong Formation constitute major gas reservoir rocks in eastern Sichuan Basin. However, the investigation with respect to sources of dolomitizing and diagenetic fluids is relatively underexplored. The current study attempts to investigate the REE characteristics of dolomites using seawater normalization standard, and therefore discusses the origins of dolomitizing and diagenetic fluids, on the basis of continuous 47.33-m-long core samples from the second member of Huanglong Formation (C2h2) in eastern Sichuan Basin. Low Th, Sc, and Hf concentrations (0.791 × 10−6, 4.751 × 10−6, and 0.214 × 10−6, respectively), random correlation between total REE concentration (ΣREE) and Fe or Mn abundance, and seawater-like Y/Ho ratios (mean value of 45.612) indicate that the carbonate samples are valid for REE analysis. Based on petrographic characteristics, four dolomite types are identified, including micritic-sized dolomite (type Dol-1), fine-to medium-sized dolomite (type Dol-2), medium-to coarse-sized dolomite (type Dol-3), and coarse-to giant-sized saddle dolomite (type Dol-4). Dol-1 dolomites, characterized by positive Ce anomaly (mean value of 6.398), light REE (LREE) enrichment, and heavy REE (HREE) depletion with mean LREE/HREE ratio of 12.657, show micritic calcite-like REE patterns, indicating seawater origin of their dolomitizing fluids. Dol-1 dolomites were formed in sabkha environment whereas the dolomitizing fluids originated from evaporative brine water due to their micritic crystal sizes and tight lithology. Dol-2 dolomites, particularly subtype Dol-2a barely developing vuggy porosity, also show micritic calcite-like REE patterns, suggesting their dolomitizing fluids were seawater or seawater-derived fluids. This inference is confirmed by low Fe and Mn concentrations, which range from 651 μg/g to 1018 μg/g (mean value of 863 μg/g) and 65 μg/g to 167 μg/g (mean value of 105 μg/g), respectively, whereas homogenization temperatures (Th, mean value of 103 °C) indicate that Dol-2 dolomites were formed under burial environment. Dol-3 dolomites, in form of cements of Dol-2 dolomites, show similar REE patterns to their host minerals (i.e., Dol-2 dolomites), indicating their parent source was possibly derived from Dol-2 dolomites. Dol-3 dolomites have high Fe and Mn concentrations with mean values of 3346 μg/g (ranging from 2897 μg/g to 3856 μg/g) and 236 μg/g (ranging from 178 μg/g to 287 μg/g), respectively, indicating the involvement of meteoric water. Meanwhile, it confirms that the dissolution in Dol-2 dolomites was caused by meteoric water leaching. Positive Eu anomalies (mean value of 1.406) in Dol-4 dolomites, coupled with high homogenization temperatures (mean value of 314 °C), suggest that Dol-4 dolomites precipitated from hydrothermal fluids. High Fe and Mn concentrations (mean values of 2521 μg/g and 193 μg/g, respectively) in Dol-4 dolomites likely results from interactions of hydrothermal fluids with deep burial clastic rocks.

Use of scanning electron microscopy for the classification of rocks of oil and gas reservoirs

With the development of electron microscopy-based porosity measurement techniques, it is possible to devise new oil and gas reservoir rock classification schemes that would take the geometrical features of the pore space into account. This is associated with the fact that the structure of the pore space of reservoir rocks has a significant effect on the recovery of hydrocarbons upon reservoir processing. For several years, we have carried out microstructural studies of rocks from the productive strata of various fields using cathodoluminescence scanning electron microscopy (SEM) and porometric software for the analysis of SEM images. The investigations show that it is possible to classify reservoirs by the connectivity of pores and pore channels in reservoir rocks.