Khair, Abul (PETRONAS Research Sdn Bhd) | Zakaria, H. (PETRONAS Research Sdn Bhd) | Ali, A. (PETRONAS Research Sdn Bhd) | R., Y. Som (PETRONAS Research Sdn Bhd) | Hady, H. (PETRONAS Research Sdn Bhd) | Baharuddin, S. (PETRONAS Research Sdn Bhd) | Goodman, A. (PETRONAS Research Sdn Bhd)
Big attention was directed towards the deepwater fields offshore Sabah area after the discovery of commercial hydrocarbons Sabah in 2002. Hundreds of wells were drilled in up-faulted structural traps within North East trending thrust ridges which some of it are dry. The interpretation of these reservoirs was established as a series of four turbidite fans from Upper Miocene to Pleistocene. Yet, no correlation was found between the same fan in different locations with regards to geometry, thickness and mineral composition. This research studied over 50,000 sqkm of 3D seismic surveys, over 100 wells with different sets of logs including image logs, cores from two wells and bathymetric images. Normal seismic structural interpretation was conducted and seismic attribute of the turbidite fans were analysed. Seabed morphology was examined using bathymetry surveys and 3D seismic. The deepwater sediments type and depositional environment were investigated using core and log data.
The geometry of the oil prone sand reservoir bodies and heterolithic sand bodies within the deepwater fields was found to be of three types: North East trending narrow sand channels and turbiditic channel levees in the Southwest area of deepwater offshore Sabah, North East trending confined turbidite sand bodies bounded by elevated structural ridges south and south east of type 1, Deepwater fan system composed of channel sand, levee turbidites and local and regional MTD to the North East of type 1
North East trending narrow sand channels and turbiditic channel levees in the Southwest area of deepwater offshore Sabah,
North East trending confined turbidite sand bodies bounded by elevated structural ridges south and south east of type 1,
Deepwater fan system composed of channel sand, levee turbidites and local and regional MTD to the North East of type 1
This new understanding of the source and sediment supply of the deepwater fields Northwest (NW) Sabah explains the geometry, distribution and lack of correlation within the Miocene sediments. Thus, this study will direct the future exploration in the deepwater reservoirs.
Sukapradja, Aldyth (Total E&P Indonesie) | Herdianto, Roni (Total E&P Indonesie) | Clark, Jesse (Total E&P Indonesie) | Adam, Cepi (Total E&P Indonesie) | Ashari, Untung (Total E&P Indonesie) | Saragih, Baginda (Total E&P Indonesie) | Sitorus, Rio (Total E&P Indonesie) | Giriansyah, Bayu (Total E&P Indonesie)
Sisi-Nubi (SNB) is a gas field located 25 km offshore from the modern Mahakam delta with overpressure reservoirs being found typically in the Sisi Main Zone (SMZ) interval. SNB 3D seismic data indicates a velocity reversal in the SMZ interval, where the overpressure occurs. This velocity reversal has a relation with location of shelf break (distal area), where beyond shelf break the NTG value is sharply decreased.
In the Mahakam area, overpressure gas reservoirs are one of the main issues in terms of drilling hazards. This has been historically managed by integrating surrounding wells' pressure data to predict the pore pressure profile that would be expected in an upcoming well. In new areas or where pressure data is lacking, it is difficult to predict the PP which can result either in heavier than necessary well architectures or an increased risk of taking a kick.
An integrated pore pressure study has been carried out on the SNB field in order to provide three dimensional and spatially continuous pore pressure prediction using four different disciplines: sedimentology, reservoir geology, geophysics and geomechanics. The integrated pore pressure model over SNB is contained within a 3D geological model where the Eaton equation can be run using following datasets: sonic well data and sedimentological trend (Well Driven model), upscaled/resampled seismic interval velocity (seismic driven model) and hybrid method as compromise between two data sources involves using the seismic data as a soft trend for the extrapolated well data (hybrid model).
Based on the blind well test analysis, the hybrid methodology shows the best result in terms of precision and 3D distribution and allows a continuous prediction of pore pressures even where there is poor well control. However, the others two methodologies could be used as an alternative when the available data is limited.
This methodology gives a new approach with more integrated information in 3D pore pressure modeling that improved the classic pore pressure prediction in field Scale and/or basin scale. However, with the remaining uncertainty and discrepancy between the DT well scale velocity and the DT seismic velocity, and considering all detail well events important inputs (Gas evolution including long connection tests, kick, pressure test, HC bouyancy and other drilling events), collaboration with a strong 1D Pore Pressure synthesis will give a comprehensive result.
Time-lapse seismic is used to monitor production for an offshore Brunei oil field (Field'M'). Several unusual observations have been made there - aquifer softening, considerable gas cap growth despite small reservoir pressure changes, and oil rim softening signals interpreted as a signature of aquifer water ingress. These observations suggested a new reservoir drive mechanism based on gas migrating from other blocks and charging gas caps.
Over recent years, many authors have proposed to compensate the absorption loss effects inside of the imaging process through the use of an attenuation model. This is necessary in the presence of strong attenuation anomalies. Q tomography has been developed for estimating this attenuation model but is generally limited to estimating attenuation in predefined anomaly areas. In this paper, we show how shallow gas pockets are revealed automatically by using a high-resolution volumetric Q tomography on the complex offshore Brunei dataset. A key component of our approach is the estimation of effective attenuation in pre-stack migrated domain through accurate picking of the frequency peak. Estimated Q-model is then used to compensate for absorption in the imaging process.
The Brunei region is considered as a complex area known for its gas escaping features over folded structures, producing shallow strong absorption anomalies. These strong anomalies seriously mask the coherency of the structure beneath.
Typically, the overall effect on the signal is that higher frequencies are dimmed more rapidly as the signal propagates through these very attenuating media. This results in a loss of signal resolution. Conversely, the attenuated signal carries additional information that can be useful in locating such gas pockets.
Measured attenuation can be compensated by applying processes such as the early techniques of inverse-Q filtering (Wang, 2002). More recently, stronger compensation due to gas or mud was included directly in the imaging process (Xie et al., 2009; Fletcher et al., 2012) through an interval Q model computed by tomography (Xin et al., 2008; Cavalca et al., 2011; Xin et al., 2014, Gamar et al., 2015). Generally, effective Q quantities are then inverted to produce a 3D interval Q model. The main purpose of tomography is to de-noise effective Q measurements in a model-consistent manner. Because the tomographic inverse problem is poorly constrained due to a difficult estimation of effective attenuation, a priori information is introduced to guide the inversion.
We present a robust workflow that uses Q tomography for converting dense inhomogeneous prestack effective Q measurements into a 3D model-consistent interval Q. To compute the effective Q volume in the pre-stack domain, we have used the method proposed by Zhang and Ulrych (2002) based on the shift of the frequency peak. Since the frequency peak (frequency at maximum amplitude) is very sensitive to the noise, we increase the signal/noise ratio by using the autocorrelation of the signal rather than the signal itself. This improves the resolution of the frequency peak value and thus the accuracy of effective Q estimation. We apply the workflow on Brunei offshore dataset to localize shallow gas pockets without any a priori information on their positions. This was made possible thanks to an adaptation to Q tomography of non-linear slope tomography (Guillaume et al., 2011) using an accurate effective Q volume picked from pre-stack migrated gathers.
Kiyashchenko, Denis (Brunei Shell Petroleum Co. Sdn. Bhd.) | Fan, Yuanzhong (Shell Projects and Technology) | Blades, Dina (Brunei Shell Petroleum Co. Sdn. Bhd.) | Geisslinger, Axel (Brunei Shell Petroleum Co. Sdn. Bhd.) | Hindriks, Folkert (Brunei Shell Petroleum Co. Sdn. Bhd.) | See, Mark (Brunei Shell Petroleum Co. Sdn. Bhd.) | Hazewinkel, Jeroen (Shell Projects and Technology)
CSEM can be used as a tool for regional exploration. However, CSEM-based prospect screening may be often mis-lead by anomalies caused by tight sediments. Integration of acoustic impedance derived from broadband seismic and CSEM helps us to identify those false anomalies and highlight the ones being potentially related to hydrocarbons. We also develop the methodology of inversion-based quantitative interpretation for CSEM and Broadband seismic data in order to quantify hydrocarbon potential and Earth resistivity uncertainty.
CSEM has been used extensively for de-risking prospects and is now rapidly emerging as a regional exploration tool that supports the detection of hydrocarbon formations. A key challenge with using CSEM for prospect identification is to differentiate HC related resistors from the non-HC related resistors and separate the “true positives” from the “false positives”. Integration with other subsurface data, such as well logs, geochemistry and the seismic underpins joined interpretation, appropriate inversion for rock properties and, finally, PoS polarization. We build upon both regional CSEM and the latest broadband seismic data to achieve this goal.
Joint CSEM and Acoustic Impedance interpretation
High resistivity foremost indicates an absence of saline formation water and can be caused by tight formations, certain lithologies, low salinity aquifers or hydrocarbon presence. Seismic data provides information on the acoustic properties of the sediments, which can be related to burial, uplift, fluid fill and overpressures for typical lithologies in Brunei acreage. For brine-saturated sands, Archie law can be used to relate electrical resistivity and acoustic impedance to porosity (see Figure 1).
Jong, John (JX Nippon Oil & Gas Exploration Corp.) | Barker, Steven (JX Nippon Oil & Gas Exploration Corp.) | Kessler, Franz L. (Petrotechnical Inspection (M) Sdn. Bhd. currently Lundin Malaysia BV.) | Tran, Quoc Tan (JX Nippon Oil & Gas Exploration Corp.)
The Bunguran Trough (BT) covering Sarawak Deepwater Block 2F shows a number of largely parallel trends of folded Neogene anticlines, with reverse faults and thrusts in the cores, and blind thrusting and folding in the upper section of the individual mapped anticlines. The Bunguran Fold Belt (BFB), comprising the deepwater deposition setting of the Rajang Delta (synonym: West Luconia Delta), has been historically compared by explorationists/geologists with the Sabah Fold Belt, and accordingly a genetic model related to gravity sliding had been advocated.
Puasa, Lenna (Brunei Shell Petroleum Co Sdn Bhd) | Hatchell, Paul (Shell International Exploration and Production) | Field, Christopher (Brunei Shell Petroleum Co Sdn Bhd) | Suut, Suria (Brunei Shell Petroleum Co Sdn Bhd) | Petter-Skogly, Odd (Brunei Shell Petroleum Co Sdn Bhd) | Kiyashchenko, Denis (Brunei Shell Petroleum Co Sdn Bhd)
4D Seismic has been identified as a key technology to optimize the Mampak field development. A high resolution baseline survey was acquired in 2006 and a dedicated 4D monitor survey in December 2012. The 4D seismic shows clear production related signals. However, the interpretation of signals in the multiple thin-stacked sand reservoirs has proven highly challenging. In this paper we discuss 4D interpretations unique to that of clastic reservoirs in the region as well as issues that need to be addressed to thoroughly understand the production related 4D signals.
The high risk near field high pressure exploration target in Maharaja Lela (MLJ) field was successfully explored which was resumed in 2007.
The successful of this exploration drilling campaign was not only rely on boldness, team work with the partners but also understanding the detail of the pressure and the architecture of the field.
Sufficient resources found has enables the project to proceed for development phase. These include building a new platform, appraisal wells and a potential additional exploration wells.
This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper IPTC 15199, "The Seria Field, Brunei: 80 Years on, Near-Field Exploration Going Strong," by John Church, SPE, and Bong Poh Yuk, Brunei Shell Petroleum, prepared for the 2011 International Petroleum Technology Conference, Bangkok, Thailand, 15-17 November. The paper has not been peer reviewed. [Note: Conference rescheduled to 7-9 February 2012.] Copyright 2011 International Petroleum Technology Conference. Reproduced by permission.
The onshore Seria oil field in Brunei was discovered in 1929 and has produced more than 1.1 billion bbl. The field still has a large near-field-exploration (NFE) portfolio of undeveloped reservoir blocks on the northern flank. These blocks, under the shallow marine surf zone, have been difficult to access because of the very shallow water and shoreward-dipping nature of the fault blocks. However, the Seria North Flank (SNF) project has begun to unlock these volumes by implementing the fishhook-well concept, allowing these opportunities to be developed from land.
The Seria oil field is a complexly faulted anticlinal structure with hydrocarbons trapped behind fault/dip structures in stacked deltaic sediments. The field straddles the coastline, with the northern half of the field offshore under shallow water. Early oil production was dominated by wells drilled on land. Production peaked at approximately 120,000 BOPD in 1956. The field production declined throughout the 1960s and much of the 1970s. Since 1990, the field has been producing approximately 20,000 BOPD.
The northern flank of the Seria anticline was known to hold hydrocarbons, but the shallow surf zone made drilling rig access problematic. Poor-quality seismic data had limited development activity. Several penetrations had been made by use of deviated wells drilled from shore, which passed orthogonally through the shoreward-dipping fault blocks with only limited and suboptimal reservoir penetration. The potential was known, but underexploited.
SNF Project (2004–09)
New high-resolution 3D seismic over the shallow marine surf zone was acquired in 1998 that identified a large number of undrilled blocks on the north flank of the Seria anticline. Exploration drilling began in 2004, with the discovery of the first block on the SNF. Follow-up drilling led to further discoveries in adjacent blocks in 2005 and 2006.
A Play Based Exploration (PBE) approach has been applied to the Brunei onshore, principle, second and third offshore agreement areas (OAA) of the Neogene (Serravalian to recent) deltaic sequences of the Baram - Balbac Basin operated by Brunei Shell Petroleum (BSP). Previous studies, utilizing a global sequence framework, are now considered to have underestimated the influence of local autocyclic forcing, manifested through high sedimentation rates, extensional delta-top tectonics and mutli-phase crustal shortening. Integration of shelf margin trajectories, biostratigraphy and structural kinematics has enabled a revised tectono-stratigraphic framework consisting of 10 major 3rd order sequences to be established in the Late Miocene to Present section. Regional compressional pulses are at the origin of some of these sequences, with syntectonic sequences showing onlap terminations on the flanks and/or thinning on the top of inverted structures and significant dislocations in the shelf edge trajectory.
A rigorous reassessment of the biostratigraphic framework has necessitated a revision of the sequence definitions and the synethsis of these observations is detailed. Two sequence boundaries are now calibrated to two major global eustatic falls (11.7 and 5.73 Ma). The 11.7 Ma event, a period of tectonic quiescence, is linked to a ~15 km basinward shift of the shelf edge trajectory without any clear sub-aerial erosion on the emerged shelf. The 5.73 Ma event, also a period of tectonic quiescence, is linked to a more modest basinward shift of the shelf edge, but accompanied by widespread canyon incision along most of the margin, and a major incision of the fluvial system feeding the Champion Delta.
Establishing a chronostratigraphic framework in deltaic sequences deposited on active margins requires a combination of pragmatism and caution. The same sequence may show very different stratal patterns and inferred systems tract along the same margin.