The effects of clay diagenesis on petrophysical properties of the lower Cretaceous sandstone reservoirs, Orange Basin, South Africa

Samakinde, Chris Adesola; Opuwari, Mimonitu; Donker, Jan van Bever

doi:10.2113/gssajg.119.1.187

Cited by 13 publications

(8 citation statements)

References 28 publications

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“…Although the pore structure of RLP is poorer and the micropores are more developed in RLP reservoir than NP reservoir, the average porosity and permeability are better. Previous researches have shown that the clay mineral is an important factor to affect reservoir physical properties (Durand et al 2001;samakinde et al 2016;Yousef et al 2018). In general, the clay minerals filling in the pores will reduce the porosity and permeability and the pore structure becomes worse.…”

Section: Discussionmentioning

confidence: 99%

Reservoir characteristics and control mechanism of resistivity low-contrast oil pays in Chang 8 tight sandstone of Longdong West area, Ordos Basin

Bai

Tan

Shi

et al. 2021

J Petrol Explor Prod Technol

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Log interpretation and evaluation of tight sandstone reservoir in Chang 8 Member of Longdong West area, Ordos Basin, China, are facing great challenges due to the co-development of normal oil pay and resistivity low-contrast oil pay. To better guide the exploration and development of oil resources in this area, the reservoir characteristics and control mechanism of resistivity low-contrast oil pay were studied. Firstly, the reservoirs were divided into resistivity low-contrast oil pay (RLP) and normal oil pay (NP) based on the relative value of the apparent resistivity increase rate. Then, the difference of reservoir characteristics between RLP and NP is analyzed by comparing a series of experimental data and real logging data in those two reservoir types. Finally, the control mechanism of RLP was studied from reservoir micro-factors and regional macro-factors, respectively. It is found that the chlorite and illite are the most abundant clay minerals in RLP and NP, respectively. Compared with NP reservoir, the average porosity of RLP is better, but the pore space is mainly composed of micropores, which lead to smaller average pore throat radius and poor pore structure. The high irreducible water saturation and high formation water salinity reduced the reservoir resistivity from micro-aspect. Besides, the difference of hydrocarbon expulsion capacity of source rock and the regional difference of formation water salinity controlled the distribution of RLP and NP. Comprehensive consideration of the reservoir micro-factors and regional macro-factors is important to carry out effective logging interpretation and evaluation.

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Section: Discussionmentioning

confidence: 99%

Reservoir characteristics and control mechanism of resistivity low-contrast oil pays in Chang 8 tight sandstone of Longdong West area, Ordos Basin

Bai

Tan

Shi

et al. 2021

J Petrol Explor Prod Technol

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“…The majority of gas shows occur in Albian sandstones (McMillan, 2003;Jungslager, 1999) whose reservoir quality has, however, been reduced in proximal parts of the basin as a result of the precipitation of quartz and illite (Samakinde et al, 2016). Hartwig (2014) showed that hydrocarbons generated from Barremian-Aptian source rocks may migrate vertically up through the overlying Cenomanian and Albian sand-rich succession until they reach Coniacian to Campanian claystones which serve as a regional seal, causing the hydrocarbons to migrate laterally.…”

Section: Petroleum Systemmentioning

confidence: 99%

Hydrocarbon Generation and Migration From Barremian – Aptian Source Rocks, Northern Orange Basin, Offshore Western South Africa: A 3d Numerical Modelling Study

Samakinde

Donker

Durrheim

et al. 2021

Journal of Petroleum Geology

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A 3D numerical modelling workflow was applied to the Barremian—Aptian source rock interval in a shelfal to lower slope area of the northern Orange Basin, offshore western South Africa. The main objective was to investigate the timing of hydrocarbon generation and migration. Hydrocarbon migration has previously been investigated in the south of the basin by relating gas escape features with structural elements as seen on seismic sections, but migration pathways are still poorly understood. The modelling study was based on data from three exploration wells (AO‐1, AE‐1 and AF‐1) together with 42 2D seismic sections totalling 3537 km in length, and a 3D seismic cube covering an area of 750 sq. km. Modelled formation temperatures increase from north to south in the study area and were consistent with downhole temperatures at well locations. However, there is variation between measured and modelled values of vitrinite reflectance (VR), especially in the Turonian and Cenomanian intervals. The measured VR is lower than the modelled VR within the Turonian section in the north of the study area, suggesting that erosion has affected the thermal maturity of the sediments. However, in the Cenomanian interval, the measured VR is higher than the modelled VR. Uplift, increased erosion in the hinterland and sediment transport to the coastal areas resulted in Cenomanian progradation of the Orange Basin fill. This together with a heat flow pulse resulted in increased thermal maturities in the study area. Modelling results show that hydrocarbon generation began in the central part of the study area by 116 Ma and reached a peak in the Late Cretaceous (65 Ma). Hydrocarbon migration began at about 110 Ma with an expulsion efficiency of 0.77. At the present day, ∼100% transformation of reactive kerogen into hydrocarbons has taken place in the central part of the study area, with random gas migration within Cenomanian and Albian reservoirs. Modelled oil migration likely influenced by hydrodynamic factors is down‐dip (westwards), towards deeper‐water, more distal parts of the basin. Gas saturation on a reactivated listric fault, which was ∼100% saturated at 93 Ma, declined to ∼15% by 65 Ma. This decrease in gas saturation is linked to uplift of the African margin in the Late Cretaceous which resulted in fault reactivation and re‐migration of gas. Despite the uncertainties which are associated with petroleum systems modelling, the study provides an insight into hydrocarbon migration in the northern part of the Orange Basin and contributes to the de‐risking of future oil and gas exploration in this area.

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“…Due to the thin-bedded argillaceous occurred in the horizontal bedded fine-grained sandstones, the calcium and silicon released by clay mineral diagenesis will result in the precipitation of calcite and quartz in the void spaces of adjacent sandstones (c.f. Mohamand and Peter, 1997;Samakinde et al, 2016;Jiu et al, 2018). It is suggested that the strong compaction of horizontal bedded fine-grained sandstones would result in the diagenetic fluid containing sufficient calcium and silicon charge into the adjacent parallel bedded fine-grained sandstones, and then the cementation was enhanced.…”

Section: The Differential Diagenesis Of Original Lithofacies Within Different Lithofacies Assembliesmentioning

confidence: 99%

The differential diagenesis controls on the physical properties of lithofacies in sandstone reservoirs from the Jurassic Shaximiao Formation, western Sichuan depression, China

Deng

et al. 2020

Journal of Petroleum Science and Engineering

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The effects of clay diagenesis on petrophysical properties of the lower Cretaceous sandstone reservoirs, Orange Basin, South Africa

Cited by 13 publications

References 28 publications

Reservoir characteristics and control mechanism of resistivity low-contrast oil pays in Chang 8 tight sandstone of Longdong West area, Ordos Basin

Reservoir characteristics and control mechanism of resistivity low-contrast oil pays in Chang 8 tight sandstone of Longdong West area, Ordos Basin

Hydrocarbon Generation and Migration From Barremian – Aptian Source Rocks, Northern Orange Basin, Offshore Western South Africa: A 3d Numerical Modelling Study

The differential diagenesis controls on the physical properties of lithofacies in sandstone reservoirs from the Jurassic Shaximiao Formation, western Sichuan depression, China

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