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.

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 Classification of Void Space Types in Fractured-Vuggy Carbonate Reservoir Using Geophysical Logging: A Case Study on the Sinian Dengying Formation of the Sichuan Basin, Southwest China

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5087
Author(s):  
Kunyu Wang ◽  
Juan Teng ◽  
Hucheng Deng ◽  
Meiyan Fu ◽  
Hongjiang Lu
Keyword(s):  
Sichuan Basin ◽  
Southwest China ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Void Space ◽  
Identification Method ◽  
Geophysical Logging ◽  
Dengying Formation ◽  
Porosity And Permeability ◽  
Core Description

The fractured-vuggy carbonate reservoirs display strong heterogeneity and need to be classified into different types for specific characterization. In this study, a total of 134 cores from six drilled wells and six outcrops of the Deng #2 and Deng #4 members of the Dengying Formation (Sichuan Basin, Southwest China) were selected to investigate the petrographic characteristics of void spaces in the fractured-vuggy carbonate reservoirs. Four void space types (VSTs) were observed, namely the solution-filling type (SFT), cement-reducing type (CRT), solution-filling breccia type (SFBT) and solution-enlarging fractures and vugs type (SEFVT). The CRT void spaces presented the largest porosity and permeability, followed by the SEFVT, SFBT and SFT. The VSTs presented various logging responses and values, and based on these, an identification method of VSTs using Bayes discriminant analysis (BDA) was proposed. Two test wells were employed for the validation of the identification method, and the results show that there is good agreement between the identification results and core description. The vertical distribution of VSTs indicates that the SFT and SEFVT are well distributed in both the Deng #2 and Deng #4 members. The CRT is mainly found in the Deng #2 member, and the SFBT occurs in the top and middle of the Deng #4 member.

Could a structurally controlled, hydrothermal dolomite play be operative in Cambro-Ordovician carbonates of the southern Georgina Basin, Queensland?

2016 ◽  
Vol 56 (2) ◽  
pp. 535
Author(s):  
Robbert J. Willink ◽  
Mike J. Bucknill ◽  
Nathan C. Palmer
Keyword(s):  
Fluid Flow ◽  
Seismic Data ◽  
Hydrothermal Fluid ◽  
Oil And Gas ◽  
Fault Zones ◽  
Tight Carbonate ◽  
Porosity And Permeability ◽  
Platform Carbonates ◽  
Hydrothermal Dolomite ◽  
Porosity Development

Hydrothermal dolomitisation of carbonates can create zones of favourable porosity and permeability in otherwise tight carbonate successions. In North America, a number of fields produce oil and gas from such reservoirs that developed along and adjacent to pre-existing fault zones acting as loci for hydrothermal fluid flow. Seismic data across these North American fields are characterised by linear zones of disturbance evident along fault zones where porosity development has occurred. Similar zones of disturbance have been observed on newly acquired seismic over the Toko Syncline in Queensland. Here, these zones extend through a thick Cambro-Ordovician carbonate succession that includes platform carbonates of the Thorntonia Limestone, overlying deeper water deposits of the Arthur Creek Formation that are organic rich and hydrocarbon generative at their base, and also in younger shallow water carbonates of the Arrinthrunga, Ninmaroo, Kelly Creek and Coolibah formations. If these zones of disturbance on seismic also reflect the development of hydrothermal dolomite reservoirs, they provide a new exploration target in the southern Georgina Basin.

Application of Techniques of Natural Fracture Characterization for Appraisal of Tight Carbonate Reservoirs: A Case Study From Jurassic of Kuwait

2021 ◽  
Author(s):  
Aishah Khalid Abdullah ◽  
Bhaskar Chakrabarti ◽  
Anas Mansor Al-Rukaibi ◽  
Talal Fahad Hadi Al-Adwani ◽  
Khushboo Havelia ◽  
...  
Keyword(s):  
Seismic Attributes ◽  
Carbonate Reservoirs ◽  
Fracture Model ◽  
Fracture Aperture ◽  
Structural Restoration ◽  
Fracture Characterization ◽  
Fracture Porosity ◽  
Tight Carbonate ◽  
Porosity And Permeability ◽  
Sweet Spots

Abstract The State of Kuwait is currently appraising and successfully developing the tight carbonates reservoirs of Jurassic age, which have very low matrix porosity and permeability. These reservoirs are affected by several tectonic events of faulting and folding, resulting in the development of interconnected natural fractures, which provide effective permeability to the reservoirs in form of production sweet spots. The objective of the study was to characterize the natural fractures and identify high permeability sweet spots as being appraisal drilling locations in a discovered field with tight carbonate reservoirs. An integrated approach was undertaken for building a discrete fracture network model by characterizing the developed faulting- and folding-related fractures and combining all subsurface data from multiple domains. The reservoir structure has a doubly plunging anticline at the field level that is affected by several strike-slip faults. The faulting-related fractures were characterized by generating multiple structural seismic attributes, highlighting subsurface discontinuities and fracture corridors. The folding-related fractures were modelled using structural restoration techniques by computing stresses resulting from the anticlinal folding. The fracture model was built in addition to the 3D matrix property model for this tight carbonate reservoir, resulting in a dual-porosity-permeability static model. Analogue data was used to compute fracture aperture and expected fracture porosity and permeability, to identify the sweet spots. Structural seismic attributes such as Ant Tracking and Consistent Dip were successful in highlighting and identifying the fault lineaments and fracture corridors. The seismic discontinuities were validated using the fractures interpreted in the image log data from the predrilled wells before being input into the fracture model. Paleo stresses, derived from structural restoration, were combined with the reservoir facies and geomechanical properties to gain important insight into predicting fractures developed due to folding. Several fracture aperture scenarios were run to capture the uncertainty associated with the computed fracture porosity and permeability. Based on the results, several sweet spots were identified, which were ranked based on their extent and connected volumes of the various permeability cases. Identifying these sweet spots helped make informed decisions regarding well planning and drilling sequence. High-inclination wells aligned parallel to the present-day maximum stress direction were proposed, which would cut across corridors of the predicted open fractures. Through this study, comprehensive fracture characterization and fracture permeability understanding of the tight carbonates in the field under study were successfully achieved. This workflow will be useful in exploratory or appraisal fields with tight carbonate reservoirs.

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.

scholarly journals Reservoir Productivity Analysis of Intercalated Limestone and Anhydrite Beds in Zagros Folded Belt, Kurdistan Region of Iraq

2020 ◽  
Vol 5 (1) ◽  
pp. 1-15
Author(s):  
Fraidoon Rashid
Keyword(s):  
Early Jurassic ◽  
Carbonate Reservoir ◽  
Fluid Distribution ◽  
Log Analysis ◽  
Productivity Analysis ◽  
Core Samples ◽  
Heterogeneous Rocks ◽  
Tight Carbonate ◽  
Jurassic Rock ◽  
Mud Logging

The Early Jurassic rock of Alan Formation in Barda Rash field has been examined using petrophysical wireline log analysis, drilling stem test, mud logging reports, drilling cutting and core samples for evaluation of reservoir potentiality and fluid production throughout heterogeneous rocks intervals in three exploration and appraisal wells. The Alan Formation consists of intercalation of light, chalky and argillaceous limestone beds with shale layers in the upper part and dominantly anhydrite layers from the middle to the lower parts of the formation. Qualitatively, weak oil shows of light brown to dark brown and blackish heavy oil have been observed while drilling. Furthermore, light brown trace oil has been recorded in the fracture surfaces of the core samples. The wireline log analysis provided an overestimated result for the hydrocarbon bearing interval identification and fluid movability index as the anhydrite layers confused the fluid distribution detection in the drilled interval. However, the combined results achieved from the mud logging reports and drilling stem tests were operated within the drilled intervals shown a limited productivity levels from the limestone beds of the Early Jurassic Alan Formation.  The oil production from the studied interval does not exceed 10% and the entire production rates were composed of formation water with a trace amount of gases. As a result, the Early Jurassic Alan Formation can be considered as a tight carbonate reservoir rocks in the Barda Rash field.

Oil Saturation Index in Hydrophobic Carbonate Reservoir: Evaluation Aspects

2021 ◽  
Author(s):  
Regina Khanbikova ◽  
Venera Bazarevskaya ◽  
Oleg Sotnikov ◽  
Albert Bachkov
Keyword(s):  
Carbonate Rocks ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Reservoir Rock ◽  
Western Slope ◽  
Void Space ◽  
The South ◽  
Reservoir Properties ◽  
Lower Carboniferous ◽  
Hydrocarbon Reserves

Abstract Hydrocarbon reserves in carbonate reservoirs account for 38% - 60% of total world reserves, according to different estimates. In Tatarstan, carbonate reservoirs are found, mostly, in the eastern slope of the Melekess Depression and the South-Tatarian Arch. The carbonate reservoirs are confined to the Middle and Lower Carboniferous sediments, the Upper Devonian (including the domanik sediments), and the Upper Permian (the Kazanian heavy oil accumulations). Considering an extensive geographic and stratigraphic range and differing tectonic and sedimentation environments, the carbonate rocks are characterized by a variety of reservoir properties. In contrast to terrigenous rocks, the carbonate void space is complicated by secondary processes that took place much later than the sedimentogenesis-lithogenesis stage. Numerous fissures, caves, sutures, and stylolites form the void space of the reservoir rock matrix containing commercial hydrocarbon reserves. In addition to fracturing and vugginess contributing to increase of void space of carbonate rocks, the secondary processes include sulphatisation and secondary dolomitization (in limestones), adding to deterioration of reservoir properties. The secondary processes impede understanding and evaluation of reservoir properties and saturation potential, in particular, determination of the oil and gas saturation factors (Dyakonova T.F. et al, 2019, Akhmetov R.T. et al, 2017)/ In the western slope of the South-Tatarian Arch, carbonate reservoirs are confined to the Middle and Lower Carboniferous sediments. Numerous RCAL and SCAL investigations provided valuable insight into these targets. In this paper, we used data from the laboratory experiments and studies of core and oil samples from the six neighbor fields on the western slope of the South-Tatarian Arch. Because of common sedimentological and tectonic sedimentation environments and lithological similarity of rocks within the stratigraphic referencing, the six fields under analysis were considered as analogous, and the results of the laboratory studies of the samples were reviewed collectively.

A Case Study of Complex Carbonate Reservoir Connectivity Analysis, Tarim Basin, China

2021 ◽  
pp. 1-41
Author(s):  
Zhangwu Meng ◽  
Zandong Sun ◽  
Guofa Li
Keyword(s):  
Tarim Basin ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Carbonate Reservoir ◽  
Carbonate Reservoirs ◽  
Connectivity Analysis ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Diffraction Imaging ◽  
Reservoir Connectivity

The connectivity of complex carbonate reservoirs has an essential impact on the exploration and development of these reservoirs. From geological genesis, the connectivity of complex carbonate reservoirs is mainly controlled by faults and dissolution. Therefore, accurate identification of faults and karst caves is the key to studying reservoir connectivity. The Ordovician carbonate reservoir in the Hudson Oilfield of the Tarim Basin is used for the reservoir connectivity analysis study. Firstly, we calculate the coherence and curvature attributes and then merge the two attributes using a neural network algorithm. Finally, we use the ant tracking method to track the faults for the merged data. The results show that the approach substantially enhances deterministic faults that can be seen directly on the seismic data, and the subtle faults can also be identified. For reservoir identification, we use the diffraction imaging method to describe the karst reservoir in this study area. The results show that diffraction imaging can identify small-scale caves that cannot be well recognized on the seismic reflection data. Furthermore, the caves connected on the diffraction seismic data are isolated from each other on the seismic reflection data, making the connection between caves clearer. Based on the results of faults and caves identification, we analyze the reservoir connectivity of the study area using the oil pressure and daily production data. It indicates that the NNW and near-NS faults probably play a role in the connection of the reservoirs, while the NEE faults tend to block the connection of the reservoirs.

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