Assessment of pore pressure, wellbore failure and reservoir stability in the Gabo field, Niger Delta, Nigeria - Implications for drilling and reservoir management

Agbasi, Okechukwu Ebuka; Sen, Souvik; Inyang, Namdie Joseph; Etuk, Sunday Edet

doi:10.1016/j.jafrearsci.2020.104038

Cited by 37 publications

(10 citation statements)

References 27 publications

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“…In this field, he also identified a stable reservoir from rock strength analysis that requires extra care during exploitation to avoid subsidence. Finally, the pore pressure gradient obtained in this study is in total agreement with the findings of Agbasi et al (2020) who obtained pore pressure gradients of 0.435psi/foot and 0.49psi/foot for lower Agbada sands and shales, respectively, while assessing pore pressure, wellbore failure, and reservoir stability in Gabo Field, Niger Delta, Nigeria.…”

Section: Discussionsupporting

confidence: 90%

Integrated 3D geomechanical characterization of a reservoir: case study of "Fuja" field, offshore Niger Delta, Southern Nigeria

Agoha

Opara

Okeke

et al. 2021

J Petrol Explor Prod Technol

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Abstract3D geomechanical characterization of "Fuja" field reservoirs, Niger Delta, was carried out to evaluate the mechanical properties of the reservoir rock which will assist in reducing drilling and exploitation challenges faced by operators. Bulk density, sonic, and gamma-ray logs from four wells were integrated with 3D seismic data and core data from the area to estimate the elastic and inelastic rock properties, pore pressure, total vertical stress, as well as maximum and minimum horizontal stresses within the reservoirs from empirical equations, using Petrel and Microsoft Excel software. 3D geomechanical models of these rock properties and cross-plots showing the relationship between the elastic and inelastic properties were also generated. From the results, Young's modulus, bulk modulus, bulk compressibility, shear modulus, Poisson's ratio, and unconfined compressive strength recorded average values of 5.11 GPa, 5.10 GPa, 0.023 GPa−1$$,$$ , 2.39 GPa, 0.39, and 39.0 GPa, respectively, in the sand, and 6.08 GPa, 6.09 Gpa, 0.016 GPa−1 2.84 GPa, 0.42, and 42.3 GPa, respectively, in shale, implying that the sand is less elastic and ductile and will deform before the shale under similar stress conditions. Results also revealed mean pore pressures of 13,248 psi and 15,220 psi in sand and shale units, respectively, mean total vertical stress of 28,193 psi, mean maximum horizontal stress of 26,237 psi, and mean minimum horizontal stress of 21,532 psi. From the geomechanical models, the rock elastic and inelastic parameters revealed higher values around the northeastern and parts of the eastern and western portions of the reservoir implying that mechanical rock deformation will be minimal in these sections of the field compared to other sections during drilling and post-drilling activities. The generated cross-plots indicate that a relationship exists between the elastic rock properties and unconfined compressive strength. Stress estimations within the reservoirs in relation to the obtained elastic and rock strength parameters show that the reservoirs are stable. These results will be invaluable in mitigating exploration and exploitation challenges.

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Section: Discussionsupporting

confidence: 90%

Integrated 3D geomechanical characterization of a reservoir: case study of "Fuja" field, offshore Niger Delta, Southern Nigeria

Agoha

Opara

Okeke

et al. 2021

J Petrol Explor Prod Technol

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“…Drilling problems caused under the uncontrolled geopressure conditions can lead to well abandonment, which costs billions of dollars to the oil and gas industry (Baouche et al, 2020;Agbasi et al, 2021). Exploration companies are putting great efforts in getting a better pore pressure prognosis for enhanced pre-drill planning to reduce non-productive time owing to geopressurerelated problems (Villacastin, 2012).…”

Section: Introductionmentioning

confidence: 99%

Overpressures Induced by Compaction Disequilibrium Within Structural Compartments of Murree Formation, Eastern Potwar, Pakistan

et al. 2022

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Overpressure conditions in Potwar Basin of Pakistan pose significant drilling and completion problems. Specifically, in eastern Potwar, abnormally high pressures are observed within structural compartments of Murree Formation of Neogene age. Compaction disequilibrium and tectonic stresses are considered as two major factors, controlling pore pressures in this foreland basin. Undercompaction of sediments due to high sediment influx affects the porosity-depth relationship as the rock deviates from the normal compaction trend. Demarcation of structural geometries is critical in understanding abnormal pressure conditions within thick molasse deposits of Murree Formation. Eastern Potwar is divided into three zones on the basis of structural geometries, including duplex thrust sheets, salt-cored anticlines, and triangular zones. Geohistory analysis and pore pressure prediction have been performed for determining the overpressuring mechanism. Log-based pressure prediction in different oil fields of eastern Potwar depicts anomalous pressure conditions in some of the wells. High-sedimentation rate during Miocene times resulted in a low porosity reduction rate due to the inability of fluid to escape out of the pores. Eaton’s method was used to predict the pore pressure, and these pressure curves were calibrated against measured pressure to validate the results. Pressures predicted in Qazian-1X well showed very good correlation with measured pressure data. Most of the wells with overpressure intervals exhibited high porosity values, showing deviation from the normal compaction trend. This pressure prediction revealed that compaction disequilibrium is the primary cause of overpressure conditions within Murree Formation, resulted in response to the rapid rate of sedimentation. The deformation mechanism and presence of different structural geometries also contributed in the development of abnormal pressures.

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“…Historically and despite decades of research into the subsurface sediment characteristics, it remains difficult to predict critical reservoir parameters of strata buried in sedimentary basins such as pore pressure (e.g., Gretener, 1979;Audet and McConnell, 1992;Martinsen, 1994;Gordon and Flemings, 1998;Dutta, 2002;Chopra and Huffman, 2006;Gutierrez et al, 2006;Zhang, 2011;Radwan et al, 2019b;Baouche et al, 2020a;Radwan et al, 2020a;Baouche et al, 2020b;Ganguli and Sen, 2020;Radwan and Sen, 2021a;Radwan, 2021b;Radwan and Sen, 2021b) and fracture pressure (e.g., Anderson et al, 1973;Traugott, 1997;Draou and Osisanya, 2000;Radwan et al, 2019b;Sen and Ganguli, 2019;Tariq et al, 2019;Radwan et al, 2020a;Radwan, 2021b). The importance of pore pressure and fracture pressure is related to their influence on drilling operations (e.g., Gray-Stephens et al, 1994;Swarbrick, 2012;Sen et al, 2020;Abdelghany et al, 2021;Radwan, 2021b), exploration (e.g., O'connor et al, 2011a;John et al, 2014), and reservoir stability and production (e.g., Hillis, 2000;Agbasi et al, 2021;Radwan and Sen, 2021a;Radwan and Sen, 2021b;Kassem et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

A multi-proxy approach to detect the pore pressure and the origin of overpressure in sedimentary basins: An example from the Gulf of Suez rift basin

Radwan

2022

Front. Earth Sci.

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The pore pressure gradient and fracture gradient (PPFG) are critical parameters for drilling mud weight design in the energy industry. Successful drilling operations can be achieved successfully through the understanding of the pore pressure and fracture pressure in the subsurface succession. The scope of this research is to use an integrated approach that encompasses well-logging, basin modeling, drilling-based interpretations, and reservoir measurement methods to gain a reasonable PPFG model and decrease the drilling uncertainties in the El Morgan oil field in the Gulf of Suez. Moreover, it investigates the overpressure generation mechanisms in the basin, which have not been studied before in this area. In this work, PPFGs of more than 16 km of cumulative thick sedimentary succession were modeled and evaluated using an integrated approach. This study utilizes Eaton’s sonic and resistivity-based methods for pore pressure evaluation, while vertical stress was calculated based on the composite density profile. The study revealed that the top geo-pressure was detected at a depth of 1,030 m of Tortonian sediments. Late Miocene sediments reveal hard over-pressure with a maximum gradient of 0.55 PSI/feet, while Middle Miocene sediments exhibit mildly over-pressured, normal, and sub-normal pore pressure zones. The lowest pore pressure values were measured in the Langhian-Serravalian Kareem reservoir with a gradient of 0.29 PSI/feet. With the exception of a slight difference in the reservoir section, the pore pressure profiles in the northern and southern parts of the El Morgan oil field are relatively similar. Reservoir connectivity is believed to be the main reason behind pore pressure magnitude differentiation in the Middle Miocene reservoirs. The key mechanism for generating overpressure has been identified as disequilibrium compaction, and reservoir overcharging may contribute as an excess-pressure generation mechanism at the reservoir level. The presented approach can be applied in PPFG studies for both development and exploratory geomechanical studies in other areas of the Gulf of Suez basin or elsewhere in the world.

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Assessment of pore pressure, wellbore failure and reservoir stability in the Gabo field, Niger Delta, Nigeria - Implications for drilling and reservoir management

Cited by 37 publications

References 27 publications

Integrated 3D geomechanical characterization of a reservoir: case study of "Fuja" field, offshore Niger Delta, Southern Nigeria

Integrated 3D geomechanical characterization of a reservoir: case study of "Fuja" field, offshore Niger Delta, Southern Nigeria

Overpressures Induced by Compaction Disequilibrium Within Structural Compartments of Murree Formation, Eastern Potwar, Pakistan

A multi-proxy approach to detect the pore pressure and the origin of overpressure in sedimentary basins: An example from the Gulf of Suez rift basin

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