Integrated approach to geopressure detection in the X-field, Onshore Niger Delta

Ugwu, S.A.; Nwankwo, Cyril N.

doi:10.1007/s13202-013-0088-4

Cited by 16 publications

(6 citation statements)

References 2 publications

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“…Below are the results of the sensitivity analysis conducted on the best model (Eaton's) using scatter plots to illustrate the correlation between the model's input variables (vertical effective stress, and sonic compressional velocities) and the desired output, figure 2 being the measured formation pore pressure (RFT) data [15]. In all the scatter plots, the points are colored using another parameter being the formation pressure gradient and the plot symbols represent the measured pressure quality [16]. The scatter plot of compressional velocity (Vp) against pore pressure (bottom left) showed that sonic compressional velocity has a strong influence on the pore pressure as both parameters increased together thereby implying a positive correlation (Figure 3).…”

Section: Sensitivity Analysis Resultsmentioning

confidence: 99%

Development of an Appropriate Model for predicting Pore Pressure in Niger delta, Nigeria using Offset Well Data

A¹,

Bello²,

Tanko³

2019

Int J Petrochem Res

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The pore pressure in most sedimentary formations such as it is in the Niger Delta, Nigeria are rarely normal. They predominantly occur as over-pressured zones, when these abnormal pressures are not predicted accurately prior to drilling, disastrous occurrences, such as kicks, and blowouts may occur. The existing models used for pore pressure predictions were developed using data outside Niger Delta environment as such a number of them yield inaccurate results. This paper provides a new approach for predicting pore pressures particularly for Niger Delta using offset well logs acquired in the Niger Delta. A number of industries utilized pore pressure prediction models were appraised using offset well data from the Niger Delta. Density and sonic velocity logs were used in generating the overburden pressure and Normal Compaction Trend. Shale trend and overburden pressure were used as inputs in the models for predicting pore pressure using RokDoc.In the development of an appropriate model for pore pressure prediction, Eaton model was modified for Niger Delta environment. Results of the model's sensitivity analysis revealed sonic velocity as the most sensitive parameter while findings from the Goal Seek analysis showed that increasing the exponent in the original Eaton's model from 3 to 3.9 yielded the most concordant result with the measured pressure data. The statistical error analysis conducted revealed that the modified Eaton's model had the least absolute mean percentage error value of 2%. Given the above results, the modified Eaton's model showed more accurate predictions when compared with existing models and will be effective in predicting pore pressure in the study area.

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Section: Sensitivity Analysis Resultsmentioning

confidence: 99%

Development of an Appropriate Model for predicting Pore Pressure in Niger delta, Nigeria using Offset Well Data

A¹,

Bello²,

Tanko³

2019

Int J Petrochem Res

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“…They observed that overpressure is prominent from 12,371.42 ft (3771.77 m) and continued to total depth. Also, [17] using Eaton's D-exponent model to predict overpressure in a Field in Niger Delta concluded that majority of overpressure situation in the area occurs between the depth of 8000 ft and 13,000 ft. These values are relatively higher than the average top of overpressure range of 6000 to 11,017 ft (TVD) obtained in this study.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Integrated Approach to Pore Pressure and Fracture Pressure Prediction Using Well Logs: Case Study of Onshore Niger-Delta Sedimentary Basin

Nwankwo¹,

Kalu²

2016

OJG

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This study investigated the cause of identified zones of overpressure in some selected wells in a field in the Niger Delta sedimentary basin. Two models were used each for predicting pore pressure and the corresponding fracture pressure using well log and drilling data. Shale lithology in Niger Delta is massive and characterized by high pore pressure; hence shale compaction theory is utilized in this study. The petrophysical data were evaluated using Ikon's Science Rokdoc software. The two major pore pressure prediction techniques employed are the Eaton's and Bowers' models while the Eaton's fracture pressure model and the Hubbert and Willis fracture pressure prediction models were utilized for fracture prediction. The density and sonic logs were used respectively to generate the shale trend and the shale normal compaction trend used for the prediction. The wells studied showed disequilibrium compaction of sediment to be the major mechanism that gave rise to overpressure in the Niger Delta. Clay diagenesis and fluid expansion were also observed as the secondary overpressure generation mechanism in well X-1. This secondary overpressure mechanism was observed to start approximately at depths of 10,000 ft (TVD). The top of overpressure and the pressure range in the wells studied varied from 6000 to 11,017 ft (TVD) and 1796.70 to 5297.00 psi respectively. The Eaton's model under-predicts pore pressure at the depth interval where unloading mechanism is witnessed. Since the study revealed presence of secondary overpressure generation mechanism, Bowers model was observed to be the most reliable pore pressure prediction model in the area.

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“…Previous studies carried out in the Niger Delta have shown that abnormal pore fluid pressure generation is related to several factors: due to disequilibrium compaction (Ichara & Avbovbo, 1985;Weber & Daukoru, 1975;Nwankwo & Kalu, 2016;Adewole et al, 2016;Udo et al, 2020;Abijah & Tse, 2016;Emudianughe & Ogagarue, 2019;Alabere & Akangbe, 2021), stratigraphic and structural controls (Evamy et al, 1978;Opara et al, 2009;Ugwu & Nwankwo, 2014) and due to normal faulting, clay diapirism, Shale diagenesis and late hydrocarbon generation (Ugwu & Nwankwo, 2014;Opara et al, 2009;Evamy et al, 1978;Nwaufa W.A., 2006;Alabere & Akangbe, 2021). These studies used well logs, seismic data and leak-off test (LOT) to predict pore pressures in the Niger Delta.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore successful drilling campaigns are achieved when the pore pressure regime within an oil basin or other geological settings is properly understood (Pwavodi & Doan, 2022). Several methods have been used to understand and characterised the pore pressure regime in the Niger Delta, yet several drilling incidences (Opara et al, 2009;Nwaufa W.A., 2006;Asedegbega et al, 2018) and overpressures have been identified within this hydrocarbon basin (Dosunmu, 2002;Opara et al, 2013;Ugwu & Nwankwo, 2014;Ichara & Avbovbo, 1985;Opara et al, 2009;Nwaufa W.A., 2006;Alabere & Akangbe, 2021).…”

Section: Introductionmentioning

confidence: 99%

Pore Pressure Prediction in Offshore Niger Delta: Implications on Drilling and Reservoir Quality

Pwavodi

Kelechi

Angalabiri

et al. 2022

Preprint

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Despite exploration and production success in Niger Delta, several failed wells have been encountered due to overpressures.Hence, it is very essential to understand the spatial distribution of pore pressure and the generating mechanism in order to mitigate the pitfalls that might arise during drilling. This research provides estimates of pore pressure along three offshore wells using the Eaton's transit time method. An accurate normal compaction trend was estimated using the Eaton's exponent (m=3). Our results show that there are three pressure magnitude regimes: normal pressure zone (hydrostatic pressure), Transition pressure zone (slightly above hydrostatic pressure), and over pressured zone (significantly above hydrostatic pressure). The top of the geopressured zone (2873 mbRT or 9425.853 ft) averagely marks the onset of overpressurization with the excess pore pressure ratios above hydrostatic pressure varying averagely along the three wells between P * = 1.06 -24.75 MPa and the lithostatic load range is λ = 0.46 -0.97 and λ * = 0.2 -0.9. The parametric study shows that the value of Eaton's exponent (m = 3-6) need to be applied with caution based on the dominant pore pressure generating mechanism in the Niger Delta. The generating mechanisms responsible for high pore pressure in the Offshore Niger Delta are disequilibrium compaction, unloading (fluid expansion) and shale diagenesis.

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Integrated approach to geopressure detection in the X-field, Onshore Niger Delta

Cited by 16 publications

References 2 publications

Development of an Appropriate Model for predicting Pore Pressure in Niger delta, Nigeria using Offset Well Data

Development of an Appropriate Model for predicting Pore Pressure in Niger delta, Nigeria using Offset Well Data

Integrated Approach to Pore Pressure and Fracture Pressure Prediction Using Well Logs: Case Study of Onshore Niger-Delta Sedimentary Basin

Pore Pressure Prediction in Offshore Niger Delta: Implications on Drilling and Reservoir Quality

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