scholarly journals Relationship between pore throat and permeability of porous carbonate reservoir in the Middle East

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Lv Miaomiao ◽  
Song Benbiao ◽  
Tian Changbing ◽  
Mao Xianyu
Keyword(s):  
Quantitative Analysis ◽  
Carbonate Rocks ◽  
Carbonate Reservoir ◽  
Accurate Estimation ◽  
Poor Correlation ◽  
Pore Throat ◽  
Throat Radius ◽  
Pore Networks ◽  
Porosity And Permeability ◽  
Pore Types

AbstractA significant behavior of carbonate reservoirs is poor correlation between porosity and permeability. With the same porosity, the permeability can vary by three orders of magnitude or more. An accurate estimation of permeability for carbonate reservoir has been a challenge for many years. The aim of this study was to establish relationships between pore throat, porosity, and permeability. This study indicates that pore throat radius corresponding to a mercury saturation of 20% (R20) is the best permeability predictor for carbonates with complex porous pore networks. Quantitative analysis was made to achieve three different patterns of pore throat for 417 carbonate samples which cover all pore types of carbonate rocks. Different relationships between porosity, pore throat radius, and permeability have been identified in different patterns, which are utilized to predict more accurate permeability by different pore throat patterns.

scholarly journals Formation environments and mechanisms of multistage paleokarst of Ordovician carbonates in Southern North China Basin

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Haitao Zhang ◽  
Guangquan Xu ◽  
Mancai Liu ◽  
Minhua Wang
Keyword(s):  
Carbonate Rocks ◽  
North China ◽  
Oil And Gas ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Geochemical Data ◽  
Near Surface ◽  
Oil And Gas Exploration ◽  
Pore Types ◽  
North China Basin

AbstractWith the reduction of oil and gas reserves and the increase of mining difficulty in Northern China, the carbonate rocks in Southern North China Basin are becoming a significant exploration target for carbonate reservoirs. However, the development characteristics, formation stages, formation environments and mechanisms of the carbonate reservoirs in Southern North China Basin are still unclear, which caused the failures of many oil and gas exploration wells. This study focused on addressing this unsolved issue from the Ordovician carbonate paleokarst in the Huai-Fu Basin, which is located in the southeast of Southern North China Basin and one of the key areas for oil and gas exploration. Based on petrology, mineralogy and geochemical data, pore types, distribution characteristics, and formation stages of the Ordovician paleokarst were analyzed. Then, in attempt to define the origins of porosity development, the formation environments and mechanisms were illustrated. The results of this study showed that pore types of the Ordovician carbonates in the Huai-Fu Basin are mainly composed of intragranular pores, intercrystalline (intergranular) pores, dissolution pores (vugs), fractures, channels, and caves, which are usually in fault and fold zones and paleoweathering crust. Furthermore, five stages and five formation environments of the Ordovician paleokarst were identified. Syngenetic karst, eogenetic karst, and paleoweathering crust karst were all developed in a relatively open near-surface environment, and their formations are mainly related to meteoric water dissolution. Mesogenetic karst was developed in a closed buried environment, and its formation is mainly related to the diagenesis of organic matters and thermochemical sulfate reduction in the Permian-Carboniferous strata. Hydrothermal (water) karst was developed in a deep-buried and high-temperature environment, where hydrothermal fluids (waters) migrated upward through structures such as faults and fractures to dissolve carbonate rocks and simultaneously deposited hydrothermal minerals and calcites. Lastly, a paleokarst evolution model, combined with the related porosity evolution processes, nicely revealed the Ordovician carbonate reservoir development. This study provides insights and guidance for further oil and gas exploration in the Southern North China Basin, and also advances our understanding of the genesis of carbonate paleokarst around the world.

Using Logging and Seismic Data to Identify Boundaries Between Different OWC Units in a Deepwater Carbonate Reservoirs

2021 ◽  
Author(s):  
Kangxu Ren ◽  
Junfeng Zhao ◽  
Jian Zhao ◽  
Xilong Sun
Keyword(s):  
Seismic Data ◽  
Carbonate Rocks ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Sedimentary Process ◽  
Core Samples ◽  
Tight Carbonate ◽  
Porosity And Permeability ◽  
Seismic Sections ◽  
Parameters Inversion

Abstract At least three very different oil-water contacts (OWC) encountered in the deepwater, huge anticline, pre-salt carbonate reservoirs of X oilfield, Santos Basin, Brazil. The boundaries identification between different OWC units was very important to help calculating the reserves in place, which was the core factor for the development campaign. Based on analysis of wells pressure interference testing data, and interpretation of tight intervals in boreholes, predicating the pre-salt distribution of igneous rocks, intrusion baked aureoles, the silicification and the high GR carbonate rocks, the viewpoint of boundaries developed between different OWC sub-units in the lower parts of this complex carbonate reservoirs had been better understood. Core samples, logging curves, including conventional logging and other special types such as NMR, UBI and ECS, as well as the multi-parameters inversion seismic data, were adopted to confirm the tight intervals in boreholes and to predicate the possible divided boundaries between wells. In the X oilfield, hundreds of meters pre-salt carbonate reservoir had been confirmed to be laterally connected, i.e., the connected intervals including almost the whole Barra Velha Formation and/or the main parts of the Itapema Formation. However, in the middle and/or the lower sections of pre-salt target layers, the situation changed because there developed many complicated tight bodies, which were formed by intrusive diabase dykes and/or sills and the tight carbonate rocks. Many pre-salt inner-layers diabases in X oilfield had very low porosity and permeability. The tight carbonate rocks mostly developed either during early sedimentary process or by latter intrusion metamorphism and/or silicification. Tight bodies were firstly identified in drilled wells with the help of core samples and logging curves. Then, the continuous boundary were discerned on inversion seismic sections marked by wells. This paper showed the idea of coupling the different OWC units in a deepwater pre-salt carbonate play with complicated tight bodies. With the marking of wells, spatial distributions of tight layers were successfully discerned and predicated on inversion seismic sections.

Improving Porosity–Velocity Relationships Using Carbonate Pore Types

2015 ◽  
Vol 23 (04) ◽  
pp. 1540006 ◽  
Author(s):  
Tingting Zhang ◽  
Yuefeng Sun ◽  
Qifeng Dou ◽  
Hanrong Zhang ◽  
Tonglou Guo ◽  
...  
Keyword(s):  
Pore Structure ◽  
Acoustic Impedance ◽  
Carbonate Rocks ◽  
Seismic Inversion ◽  
Carbonate Reservoir ◽  
Reservoir Rocks ◽  
Fluid Content ◽  
Fracture Fluid ◽  
Poroelastic Model ◽  
Pore Types

Acoustic impedance in carbonates is influenced by factors such as porosity, pore structure/fracture, fluid content, and lithology. Occurrence of moldic and vuggy pores, fractures and other pore structures due to diagenesis in carbonate rocks can greatly complicate the relationships between impedance and porosity. Using a frame flexibility factor ([Formula: see text]) derived from a poroelastic model to characterize pore structure in reservoir rocks, we find that its product with porosity can result in a much better correlation with sonic velocity ([Formula: see text] = [Formula: see text]) and acoustic impedance ([Formula: see text] = [Formula: see text], where A, B, C and D is 6.60, 0.03, 18.3 and 0.09, respectively for the deep low-porosity carbonate reservoir studied in this paper. These new relationships can also be useful in improving seismic inversion of ultra-deep hydrocarbon reservoirs in other similar environments.

scholarly journals Fuzzy Logic in Carbonate Reservoir Quality Assessment: A Case Study from Tarim Basin, China

2017 ◽  
Vol 10 (1) ◽  
pp. 195-203
Author(s):  
Weifu Liu
Keyword(s):  
Fuzzy Logic ◽  
Quality Assessment ◽  
Tarim Basin ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Reservoir Quality ◽  
Pore Throat ◽  
Throat Radius ◽  
Single Well ◽  
Factor Set

Introduction: To address reservoir quality assessment in highly complex and heterogeneous carbonate reservoirs, a methodology utilizing fuzzy logic is developed and presented in this paper. Based on carbonate reservoir characteristics, three parameters reflecting the macroscopic and microscopic of storage abundance, permeability, and median of pore throat radius were selected to establish the factor set and the evaluation criteria. After analysis of core and test data, a membership function is constructed by semi-drop trapezoid method and the weight formula is also determined by reservoir factor sub-index. The developed method then is used to evaluate a carbonate reservoir in the Tarim Basin in China. Based on the result of single well evaluation, the plane classification map of the carbonate reservoir quality is constructed. Results obtained from reservoir quality assessment in the K32 well show that I-level, II-level, and III-level reservoir qualities account for 58%, 37%, 5% of the reservoir, respectively. The results are consistent with the actual production data demonstrating reliability of the proposed method for reservoir quality assessment practices in usually very complex and heterogeneous carbonate reservoirs. Background: Carbonate reservoirs are complex and heterogeneous and this makes their evaluation a difficult task. Objective: To overcome the uncertainties associated with evaluation of complex carbonate reservoirs a reliable method to accurately evaluate carbonate reservoirs is presented. Methods: Fuzzy logic is used to evaluate a carbonate reservoir from Tarim Basin in China. Based on carbonate reservoir characteristics, three parameters reflecting the macroscopic and microscopic of storage abundance, permeability, and median of pore throat radius are selected to establish the factor set and to evaluate the criteria of carbonate reservoir. After the analysis of core and test data, a membership function is reasonably constructed by semi-drop trapezoid method and the weight formula is also determined by reservoir factor sub-index. Results: An effective methodology for the evaluation of reservoir quality in carbonate reservoirs is established by using fuzzy logic. In addition, an example reservoir from China is used to demonstrate the applicability of the developed method. Conclusion: Based on the result of single well evaluation, the plane classification map of the carbonate reservoir is constructed. Favorable zones in the reservoir are also delineated. Evaluation results are consistent with the actual production data of gas and oil which proves that the proposed method is instrumental in reservoir quality assessment.

scholarly journals Optimization of Rock Physics Models by Combining the Differential Effective Medium (DEM) and Adaptive Batzle-Wang Methods in “R” Field, East Java

2019 ◽  
Vol 17 (2) ◽  
Author(s):  
M. Wahdanadi Haidar ◽  
Reza Wardhana ◽  
M. Iskan ◽  
M. Syamsu Rosid
Keyword(s):  
Elastic Modulus ◽  
Wave Velocity ◽  
Carbonate Rocks ◽  
Effective Medium ◽  
Carbonate Reservoir ◽  
P Wave ◽  
S Wave ◽  
P Wave Velocity ◽  
Reservoir Conditions ◽  
Pore Types

The pore systems in carbonate reservoirs are more complex than the pore systems in clastic rocks. There are three types of pores in carbonate rocks: interparticle pores, stiff pores and cracks. The complexity of the pore types can lead to changes in the P-wave velocity by up to 40%, and carbonate reservoir characterization becomes difficult when the S-wave velocity is estimated using the dominant interparticle pore type only. In addition, the geometry of the pores affects the permeability of the reservoir. Therefore, when modelling the elastic modulus of the rock it is important to take into account the complexity of the pore types in carbonate rocks. The Differential Effective Medium (DEM) is a method for modelling the elastic modulus of the rock that takes into account the heterogeneity in the types of pores in carbonate rocks by adding pore-type inclusions little by little into the host material until the required proportion of the material is reached. In addition, the model is optimized by calculating the bulk modulus of the fluid filler porous rock under reservoir conditions using the Adaptive Batzle-Wang method. Once a fluid model has been constructed under reservoir conditions, the model is entered as input for the P-wave velocity model, which is then used to estimate the velocity of the S-wave and the proportion of primary and secondary pore types in the rock. Changes in the characteristics of the P-wave which are sensitive to the presence of fluid lead to improvements in the accuracy of the P-wave model, so the estimated S-wave velocity and the calculated ratio of primary and secondary pores in the reservoir are more reliable.

Predicting subsurface CO2 movement: From laboratory to field scale

Geophysics ◽  
2012 ◽  
Vol 77 (3) ◽  
pp. M27-M37 ◽  
Author(s):  
Ranjana Ghosh ◽  
Mrinal K. Sen
Keyword(s):  
Elastic Properties ◽  
Carbonate Rocks ◽  
Water Saturation ◽  
Time Lapse ◽  
Carbonate Reservoir ◽  
S Wave ◽  
Permeability Enhancement ◽  
Proposed Model ◽  
Porosity And Permeability ◽  
Frequency Dependent Model

Finding an appropriate model for time-lapse seismic monitoring of [Formula: see text]-sequestered carbonate reservoir poses a great challenge because carbonate-rocks have varying textures and highly reactive rock-fluid system. We introduced a frequency-dependent model based on Eshelby’s inclusion and differential effective medium (DEM) theory that can account for heterogeneity in microstructure of rocks and squirt flow. We showed that the estimated velocities from the modified DEM theory match well with the laboratory measurements (ultrasonic) of velocities of carbonate rocks saturated with [Formula: see text]-rich water. The theory predicts significant decrease in saturated P- and S-wave velocities in the seismic frequency band as a consequence of porosity and permeability enhancement by the process of chemical dissolution of carbonates with the saturating fluid. The study also showed the combined effect of chemical reaction and free [Formula: see text] saturation on the elastic properties of rock. We observed that the velocity dispersion and attenuation increased from complete gas saturation to water saturation. The proposed model can be used to invert geophysical measurements to detect changes in elastic properties of a carbonate reservoir and interpret the extent of [Formula: see text] movement with time. These are the key elements to ensure that sequestration will not damage underground geologic formation and [Formula: see text] storage is secure and environmentally acceptable.

Pore structure and fluid uptake of the Yeso, Abo, and Cisco Formations in the Permian Basin in southeast New Mexico, USA

2019 ◽  
Vol 7 (4) ◽  
pp. SK1-SK17 ◽  
Author(s):  
Qinhong Hu ◽  
Griffin Mann ◽  
Jianhua Zhao
Keyword(s):  
Contact Angle ◽  
New Mexico ◽  
Pore Structure ◽  
Water Saturation ◽  
The Other ◽  
Rock Surface ◽  
Pore Throat ◽  
Pore Networks ◽  
Fluid Uptake ◽  
Porosity And Permeability

There is a need for a petrophysical understanding of producing formations in the Northwest Shelf in southeast New Mexico. Working with six rotary sidewall core samples (dolomite, limestone, and sandstone), we have investigated the utility of mercury injection capillary pressure (MICP), contact angle, fluid imbibition, as well as logging analyses to evaluate the characteristics of pore structure and fluid uptake of the Yeso (Paddock and Blinebry members), Abo, and Cisco Formations. Results from MICP tests provide a variety of pore structure data including bulk and particle densities, porosity, pore-throat size distribution, permeability, and tortuosity. Two Abo dolomite samples indicate the highest porosities at greater than 15%, compared with 4%–7% for the other two dolomite samples from the Paddock and Blinebry members within the Yeso Formation. Most of the pore-throat sizes for these samples fall within the range of [Formula: see text]. The only exceptions are the Paddock member sample, which possesses a higher percentage of larger pores ([Formula: see text]), and the dolomite sample from the Cisco Formation, which has most of its pore-throat sizes falling within the range of [Formula: see text]. From contact angle measurements, all samples are found to be oil-wet because n-decane spreads onto the rock surface much quicker than the other hydrophilic fluids (deionized water and brine). Imbibition tests reveal well-connected pore networks in all samples, with the highest values of imbibition slopes being recorded for the Abo samples. In addition, we used the crossplot of porosity and water saturation obtained from log analyses to derive a value for permeability at field scales. The porosity and permeability values, from log analyses as well as laboratory MICP and gas pycnometry-permeameter measurements, and at different observational scales, are generally consistent. The overall results provide a snapshot of the pore structure characteristics, from limited samples but using integrated approaches and scales, of these formations.

scholarly journals Calculation of Pore Throat Radius Percentiles (25, 50 & 75) From Porosity and/or Permeability: Algyo Oil and Gas Field, Hungary

2021 ◽  
Vol 906 (1) ◽  
pp. 012004
Author(s):  
Nahla A. El Sayed ◽  
El sayed Abdel Moktader A.
Keyword(s):  
Size Distribution ◽  
Oil And Gas ◽  
Reservoir Characterization ◽  
Size Analysis ◽  
Pore Throat ◽  
Throat Radius ◽  
Gas Field ◽  
Reservoir Rocks ◽  
Oil And Gas Field ◽  
Porosity And Permeability

Abstract Pore throat size distribution of reservoir rocks has a great importance in hydrocarbon migration and entrapment. It is used for study permeability barriers, reservoir characterization and stratigraphic traps. In the present study 51 core samples obtained from Algyo oil and gas field were conducted to MICP laboratory technique to study pore throat size distribution. The inclusive graphical measures of gain size analysis were borrowed for pore throat size examination. Various pore throat radius percentiles such as 25,50 and 75 were calculated and related to both rock porosity and permeability. The obtained models were robust and reliable to use for pore throat radius percentiles (25,50 and 75) calculation. One of these models which is predicting the 50 percentiles was verified. It shows reliable coefficients of correlation (R2 = 0.77 and 0.79) as it is estimated from permeability and porosity, respectively.

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