Using a multi-strand approach to shale pressure prediction, shallow offshore Niger Delta

Aikulola, Understanding; Asedegbega, Jerome; O'Connor, Steve; Swarbrick, Richard E.; Scott-Ogunkoya, Olusola; Anaevune, Austin; Olotu, Sam

doi:10.1190/segam2013-1390.1

Cited by 3 publications

(2 citation statements)

References 3 publications

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“…4,5) and attesting to the fact that a single method may lead to ambiguity based on the abnormal pore pressure regime and complex geology. A multi-strand approach is most suitable in such situation (Aikulola et al 2013), and thus, Vp-VES relationship derived for both the loading and unloading scenarios was used to validate the Eaton's exponents (Figs. 4, 5).…”

Section: Resultsmentioning

confidence: 99%

A method to reduce the uncertainty of pressure prediction in HPHT prospects: a case study of Onshore Niger Delta depobelt, Nigeria

Asedegbega

Oladunjoye

Nwozor

2017

J Petrol Explor Prod Technol

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The search for hydrocarbons has gone beyond shallow hydrostatic reservoirs, necessitating deep drilling beyond known depths in the mature Onshore Niger Delta fields. Often times, the challenge has been the ambiguity in pore pressure prediction beyond the shallow depths where disequilibrium compaction is no longer the active overpressure contributor. This leads to underbalanced drilling with the implication that well drilling is terminated at the occurrence of the first kick, before reaching the target depth. Thus, in this study, the dominant overpressure mechanism is determined by the analyses of velocity, density versus depth cross-plots. The Eaton empirical approach, equivalent depth method (EDM), a deterministic approach, and Bowers velocity-vertical effective stress (Vp-VES) relationship were applied to Vp-sonic log to compare prediction profiles. Pressure data were used to infer geologically consistent Eaton's exponents and Vp-VES curve for loading and unloading scenarios. The results show that deeper than the approximately 11,000 ft where unloading began, EDM and Eaton's exponent of 3.0 would fail. However, higher exponents can be adopted for the area at onset of unloading temperatures ranging from 98 to 100°C. The estimated shale pressure profile from the EDM, Eaton's exponents and Vp-VES models accurately fit the measured pressure data. In that way, the uncertainty in the prediction can be quantified. Hence, predrill estimates of shale pressures can be generated beyond known depths since the model can be used to transform seismic velocity to formation pressure, thereby ensuring better anticipation of potential risks and cost-effective drilling.

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Section: Resultsmentioning

confidence: 99%

A method to reduce the uncertainty of pressure prediction in HPHT prospects: a case study of Onshore Niger Delta depobelt, Nigeria

Asedegbega

Oladunjoye

Nwozor

2017

J Petrol Explor Prod Technol

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“…These depobelts form one of the largest regressive deltas in the world with an area of some 300,000 km 2 [6], a sediment volume of 500,000 km 3 [7], and a sediment thickness of over 10 km in the basin depocenter [8]. Most of the thick shales are within the Akata Formation, and this section is the habitat of high overpressures and temperatures observed in the onshore area [9]. The Niger Delta Province contains only one identified petroleum system [6,10].…”

Section: Geology Of Niger Deltamentioning

confidence: 99%

Investigating the Subsurface Pressure Regime of Ada-field in Onshore Niger Delta Basin Nigeria

Je¹,

Do²

2018

J Geol Geophys

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Pore Pressure Prediction (PPP) has been proven to be more difficult in basins like the Niger Delta where the subsurface pressure system is complex. Failure of PPP practioners to recognize lateral and vertical variations of formation pressure even within the immediate vicinity of local geology had led to greater uncertainty and safety threat in drilling activities. Hence; this work attempted to investigate subsurface pressure pattern in Ada field, on Onshore Niger Delta depositional belt. Wireling logs, mud weights and reservoir pressures from four wells were analysed for this purpose. The overpressure in field is seen to be mild, i.e. below 0.5 psi/ft but it exceeded 0.6 psi/ft at depth ~12000 ft TVDml with overpressure magnitude of 1682 psi. The study revealed the effect of hydrocarbon production in the field as indicated by drained reservoir pressures. The field is seen to have high net-to-gross ratio as it is common with wells that penetrate the Benin Formation. Result shows that reservoir pressures and that of adjacent shales are not equilibrium hence; caution must be taken when using any offset well as a proxy to pore pressure calculation in the studied area. With is information, it will be easier for PPP experts to estimate pore pressures accurately in these intervals and prevent the risk of drilling dry holes in future exploration activities in the area.

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Application of in-situ anisotropic parameters in 3D seismic velocity analysis for improved pre-drill pore pressure prediction in the onshore Niger Delta basin, Nigeria

et al. 2021

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Using a multi-strand approach to shale pressure prediction, shallow offshore Niger Delta

Cited by 3 publications

References 3 publications

A method to reduce the uncertainty of pressure prediction in HPHT prospects: a case study of Onshore Niger Delta depobelt, Nigeria

A method to reduce the uncertainty of pressure prediction in HPHT prospects: a case study of Onshore Niger Delta depobelt, Nigeria

Investigating the Subsurface Pressure Regime of Ada-field in Onshore Niger Delta Basin Nigeria

Application of in-situ anisotropic parameters in 3D seismic velocity analysis for improved pre-drill pore pressure prediction in the onshore Niger Delta basin, Nigeria

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