scholarly journals Reactive Transport Simulation of Cavern Formation along Fractures in Carbonate Rocks

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 38
Author(s):  
Ruiqi Duan ◽  
Genhua Shang ◽  
Chen Yu ◽  
Qiang Wang ◽  
Hong Zhang ◽  
...  
Keyword(s):  
Carbonate Rocks ◽  
Reactive Transport ◽  
Oil And Gas ◽  
Characteristic Length ◽  
Fracture Network ◽  
Oil And Gas Exploration ◽  
The Matrix ◽  
Complex Fracture Network ◽  
Matrix Porosity ◽  
Porosity Heterogeneity

Karst cavities and caves are often present along fractures in limestone reservoirs and are of significance for oil and gas exploration. Understanding the formation and evolution of caves in fractured carbonate rocks will enhance oil and gas exploration and development. Herein, a reactive transport model was established considering both the matrix and fractures. Different factors affecting the dissolution along fractures were considered in the simulation of matrix–fracture carbonate rocks, including the magnitude and characteristic length of the matrix porosity heterogeneity, intersecting fractures, and complex fracture network. The results show that a strong heterogeneity of the matrix porosity significantly affects the cave formation along the fracture and the existence of fractures increases the heterogeneity due to the high permeability as well as the dissolution area. The characteristic length of the matrix porosity heterogeneity affects the cave location and shape. The larger permeability of intersecting fractures or the matrix greatly increases the cave size, leading to the formation of large, connected cave areas. A complex fracture network leads to more developed karst dissolution caves. The topology of the fracture network and preferential flow dominate the distribution of caves and alleviate the effect of the matrix heterogeneity.

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.

scholarly journals Static Geological Modelling with Knowledge Driven Methodology

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3802
Author(s):  
Jun Li ◽  
Xiaoying Zhang ◽  
Bin Lu ◽  
Raheel Ahmed ◽  
Qian Zhang
Keyword(s):  
Case Studies ◽  
Oil And Gas ◽  
Fracture Network ◽  
Depositional Environments ◽  
Soft Data ◽  
Oil And Gas Exploration ◽  
Hard Data ◽  
The North ◽  
Geological Modelling ◽  
Exploration And Production

Geological modelling is an important topic of oil and gas exploration and production. A new knowledge driven methodology of geological modelling is proposed to address the problem of “hard data” limitation and modelling efficiency of the conventional data driven methodology. Accordingly, a new geological modelling software (DMatlas) (V1.0, Dimue, Wuhan, China) has been developed adopting a grid-free, object-based methodology. Conceptual facies models can be created for various depositional environments (such as fluvial, delta and carbonates). The models can be built largely based on geologists’ understandings with “soft data” such as outcrops analysis and geological maps from public literatures. Basic structures (fault, folds, and discrete fracture network) can be easily constructed according to their main features. In this methodology, models can be shared and re-used by other modelers or projects. Large number of model templates help to improve the modelling work efficiency. To demonstrate the tool, two case studies of geological modelling with knowledge driven methodology are introduced: (1) Suizhong 36-1 field which is a delta depositional environment in Bohai basin, China; (2) a site of the north Oman fracture system. The case studies show the efficiency and reliability within the new methodology.

Study on Hydrocarbon Source Rocks with Accumulation Characteristics Research of Camck-Aral Sea

2013 ◽  
Vol 703 ◽  
pp. 139-142
Author(s):  
Hui Ting Hu ◽  
Hai Tao Xue ◽  
Xiang Qi Kong ◽  
Hong Peng Yao
Keyword(s):  
Middle Jurassic ◽  
Oil And Gas ◽  
Source Rocks ◽  
Aral Sea ◽  
Maturity Stage ◽  
Hydrocarbon Source Rock ◽  
Oil And Gas Exploration ◽  
Hydrocarbon Source Rocks ◽  
The Matrix ◽  
Reservoir Conditions

Camck-Aral sea is one of the important China's developing overseas oil and gas exploration blocks. But conditioned by the degree of exploration, the hydrocarbon source rocks quality and resource potential of this block are not clear. Therefore, in this study, we analyzed the regional geological survey, hydrocarbon source rock condition and reservoir conditions. The results indicated that: The middle Jurassic formation in Camck-Aral sea block has a texture of interbeded sandstones and mudstones. Middle Jurassic hydrocarbon source rocks in Camck-Aral sea block is high in the abundance of organic matter,of which the matrix belongs to the type II2, and it has reached the maturity stage. This may mean that the study area should be based primarily on natural gas exploration.

Artificial Neural Networks Identification of Lithology-Types in Complex Carbonate from Well Logs, Block K, in Uzbekistan

2013 ◽  
Vol 756-759 ◽  
pp. 2396-2400 ◽  
Author(s):  
Ya Ping Lin ◽  
Tie Zhuang Wu ◽  
Xiao Feng Sheng ◽  
Chun Sheng Wang ◽  
Tian Wei Zhou
Keyword(s):  
Quantitative Evaluation ◽  
Carbonate Rocks ◽  
Oil And Gas ◽  
Positive Role ◽  
Oil And Gas Exploration ◽  
Response Characteristics ◽  
Lithology Identification ◽  
Artificial Neural Network Analysis ◽  
Artificial Neural ◽  
Mud Logging

In oil and gas exploration of Block K in Amu Darya basin Uzbekistan, the reservoir lithologies are mainly in different carbonate rocks, the more types of rocks, the more various reservoir space is, as a result, it brings some difficulties to the reservoir quantitative evaluation. Therefore, according to this situation that the difficulty in identification of complex carbonate lithologies is, in this study block, artificial neural network analysis method is used in this paper. The method combines mud logging, cutting, core data, well logging, studies logging response characteristics of the different types of carbonate rocks, establishes lithology identification index. In this study, the method is used in identifying the types of carbonate rocks, the identified result compared to actual rocks displays about 70.51~87.23%, and it plays the positive role for reservoir quantitative evaluation.

Modeling and experimental investigation of the evolution of altered zones at the shale-fluid interface

2020 ◽  
Author(s):  
Hang Deng ◽  
Sergi Molins ◽  
Carl Steefel ◽  
John Bargar ◽  
Adam Jew ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Reactive Transport ◽  
Oil And Gas ◽  
Transport Model ◽  
Gas Production ◽  
Production Performance ◽  
Fracture Permeability ◽  
Oil And Gas Production ◽  
Fracturing Fluids ◽  
The Matrix

<p>Unconventional oil and gas production involves the use of acidic hydraulic fracturing fluids that interact with the rock matrix bordering the fractures. As a result, fracture permeability and mass transfer between the matrix and the fracture can be altered, affecting production performance. The evolution of the altered zones are controlled by the gradients of pH and concentrations of various species perpendicular to the fracture-matrix interface, mineral reactions in the matrix as the reactive fluid diffuse into the matrix, and potential mineral coating on the fracture surface where the matrix fluid and fracture fluid mix. In this study, we use reactive transport model to investigate the evolution of the altered zones bordering the fractures. The simulations are based on batch and fracture flow experiments of shales and syntheized hydraulic fracturing fluids. Through the simulations, we quantify the reaction front of different mineral phases and the change of local porosity, and examine their dependence on mineral composition and fluid chemistry. We also discuss the impacts of the altered zones on matrix diffusivity and fracture permeability.</p>

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