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Rapid production decline of a mature brown field with high density of oil wells has triggered the need to search for trapped and undrained oil to arrest the decline. The field, ABC is located within the Malay Basin offshore Peninsular Malaysia and has been producing since 2002 with 40% reserves already drained. Recent reservoir studies have shown that oil pockets trapped in structural highs in water flooded reservoir and in structural lows in reservoirs with thick gas cap are unable to be drained with existing wells. Horizontal wells, with the aid of well placement technology were drilled to realise the potentials and increase field production.
An integrated approach utilising data from reservoir static and dynamic models and seismic interpretation were used to identify targets in areas of structural highs and lows. Economically viable prospects were selected based on remaining reserves, sand thickness, structure, fluid contacts and locations of nearby water injectors/producers and confirmed by a pilot hole. Based on the results, horizontal well placement is designed with the aid of an imaging tool using resistivity inversion to identify the base or roof of sand to ensure optimum standoff from fluid contacts to prevent early water encroachment or premature gas coning.
Two (2) horizontal wells were drilled with this approach. The first well, X targets 7m of oil column in a structural high bounded by oilwater contact and downdipping top of sand. The pilot hole confirmed presence of oilbearing sand and well placement technology was deployed to geosteer the horizontal section. A 200m horizontal section was drilled 3m above oilwater contact resulting in production of 1500 bbl/day. The second well, Y targets 6m of oil column in a structural low bounded by gasoil contact and updipping base of sand. 70m of oilbearing horizontal section was drilled with 0.5m standoff from the base channel resulting in production of 1000 bbl/day. The usage of well placement technology has aided the subsurface team in landing the horizontal section by navigating the undulations at the base and top of the channel at a scale unresolved by seismic resolution. By analogue, the resistivity inversion confirmed the rugosity of base and top of channel sand in many similar clastic reservoirs. Due to the dynamic of producing reservoir and variability in reservoir quality, the observed fluid contacts are also different for different oil pockets in the same reservoir highlighting the risks that need to be considered when proposing future targets. This strategy coupled with the well placement technology has allowed the realisation of otherwise stranded few MMstb oil in this brown field. This strategy can be replicated for clastic reservoirs in mature brown fields around the globe facing a rapid decline in production.
Peter, Obidike (University of Port Harcourt World Bank Africa Centre of Excellence for Oilfield Chemicals Research and Shell Petroleum Development Company) | Onyekonwu, Mike (University of Port Harcourt World Bank Africa Centre of Excellence for Oilfield Chemicals Research) | C. E., Ubani (University of Port Harcourt World Bank Africa Centre of Excellence for Oilfield Chemicals Research)
In this paper, review findings from past literature on development of thin oil rim reservoirs are presented. The review entailed going through several papers written in the subject with a view to identifying possible research gaps with opportunity of proffering solutions. The review areas that require attention include; proper definition of thin oil rim reservoir, inadequacy of the current classification of factors that affect oil rim development by non-consideration of strategic, commercial and stakeholder aspects. Other areas include; non-application of a combined depletion and flooding scheme under critical flow conditions in the Niger Delta and non-focus on controllable factors in the use of engineering design in the evaluation of thin oil rim reservoir development options. Hence in this paper we proffer thoughts on a rational definition of a "Thin oil rim reservoir", highlight some development schemes termed "novel" in this study and propose such applications in evaluation of thin oil rim reservoirs especially in the Niger Delta. The evaluation of these options suffixes as evidence that due diligence has been made in a bid to ensure a robust development plan.
Ahmad Tajuddin, Nor Baizurah (PETRONAS Carigali Sdn. Bhd.) | Dan, Hui Xuan (PETRONAS Carigali Sdn. Bhd.) | Tusimin, Fuziana (PETRONAS Carigali Sdn. Bhd.) | Kawar, Saraton (PETRONAS Carigali Sdn. Bhd.) | Riza Feisal, Sheikh M. Razi (PETRONAS Carigali Sdn. Bhd.) | Wahid Ali, Nurul Athirah (PETRONAS Carigali Sdn. Bhd.) | M. Shah, Jamari (PETRONAS Carigali Sdn. Bhd.) | Riyanto, Latief (PETRONAS Carigali Sdn. Bhd.) | Hussain, Mansoor (PETRONAS Carigali Sdn. Bhd.) | A'Akif Fadzil, Nurul Aula (PETRONAS Carigali Sdn. Bhd.) | Sakdilah, M. Zaki (PETRONAS Carigali Sdn. Bhd.)
The scope of the paper is to share a case study of a successful horizontal well completed within an extremely thin oil rim of ~10ft with bottom water. This paper highlights the differentiating activities undertaken to deliver the well despite the challenges of extremely thin oil rim, strong water drive and uneven current fluid contacts.
Prior to drilling this well, attempt was made to mitigate the uncertainty regarding the current gas-oil contact (GOC) and oil-water contact (OWC) by carrying out cased-hole logging in some of the adjacent wells, and re-sequencing and re-optimizing the location of two of the wells targeting the reservoirs below. This obviated the need for the pilot hole and thereby resulted in a cost saving of ~USD 1Million. Furthermore, the dynamic simulation model was updated to create a fit-for-purpose model with the latest OWC and GOC, so as to be able to test various trajectories.
While drilling, the well was drilled with real-time reservoir mapping-while-drilling technology and integrated with real-time reservoir characterization, fluid typing and trajectory modification, while maintaining Dog Leg Severity (DLS) below 3 deg/100ft for the ease of completion run.
Completion was then optimized with viscosity-based inflow control orifices. Post drilling, dynamic and well models were calibrated to the actual results to determine optimum production rate for the well life.
The horizontal well was successfully navigated and optimally placed in the extremely thin oil column. Tilted contacts were encountered in the targeted subunits where actual current contacts came in ~20ft shallower at heel and ~10ft deeper at toe compared to prognosis. Consequently, the heel landed at a 5ft stand-off from water, and the toe landed 18ft stand-off from water and 6ft stand-off from gas.
The well was successfully unloaded and tested at a controlled oil rate of 2887 bopd, 50% higher than planned target.
This paper presents the entire process from well planning until well production tie-in. This was achieved through the integration of subsurface understanding with the utilization of the appropriate technology. Finally, the management's trust in the capability of the team members ensured deliverability of the target production rate and the consequent booked reserves.
Obidike, Peter (University of Port Harcourt World Bank Africa Centre of Excellence for Oilfield Chemicals Research and Shell Petroleum Development Company) | Onyekonwu, Mike (University of Port Harcourt World Bank Africa Centre of Excellence for Oilfield Chemicals Research) | Ubani, C. E. (University of Port Harcourt World Bank Africa Centre of Excellence for Oilfield Chemicals Research)
In this paper one of the areas of conflicts observed with the performance of horizontal wells standoff with respect to development of thin oil rim reservoirs is examined. In a technical paper as part of the critical review of literature on the exploitation of thin oil rim reservoirs with large gas cap and aquifer, this author had highlighted the problem. As part of sensitives in horizontal well standoff, Cosmos and Fatoke (2004) tested three positions; one-third, centre and two-third positions from the GOC in a Niger Delta field. They concluded that the landing closest to the GOC (one-third position) yielded lowest Oil compared to the centre and two-third positions. Surprisingly the work done by Sai Garimella et al (2011) in a 60ft Ghariff & Al Khlata shallow marine low permeability sandstone reservoirs in a field in Oman showed a different result with the one-third position indicating an optimum recovery from a horizontal well. Interestingly both authors positions on the performance had support from other authors. This study used a 3D reservoir model, investigated different horizontal well standoff performances and applied permeability reduction to simulate different reservoir quality.
Imomoh, Victor (Baker Hughes, a GE company) | Ndokwu, Chidi (Baker Hughes, a GE company) | Amadi, Kenneth (Baker Hughes, a GE company) | Toyobo, Oluwaseun (Baker Hughes, a GE company) | Nwabueze, Ikechukwu (Baker Hughes, a GE company) | Okowi, Victor (Baker Hughes, a GE company) | Ajao, Oyekunle (Chevron Nigeria Limited.) | Okeke, Genevieve (Chevron Nigeria Limited.) | Dada, Yemi (Chevron Nigeria Limited.) | Jumbo, Sandison (Chevron Nigeria Limited.) | Aina, Soji (Chevron Nigeria Limited.)
Oil and gas drilling has fully embraced the practice of drilling horizontal and extended-reach wells in place of deviated wells to avoid multi-platform drilling and increase hydrocarbon recovery. However, the producer is still faced with multiple challenges that include lateral facies change, lateral variation in reservoir properties and structural uncertainties. Consequently, it is paramount that continuous advancement is achieved in combining fit-for-purpose, real-time logging-while-drilling (LWD) solutions to assist further in the enhancement of hydrocarbon recovery.
Reservoir navigation services (RNS) involve predicting the geology ahead of the bit to place the wellbore correctly in the zone of interest in a horizontal or near-horizontal path. LWD data, obtained from downhole drilling suites, transmitted in real time through mud pulses to a surface computer where the data are interpreted and used to steer the well in the desired direction. Formation pressure while drilling (FPWD) is a process of acquiring reservoir pressures downhole and this is done with a specialized downhole LWD pressure-testing tool. The use of RNS in Well-MX played a significant role in the drilling project – landing Well-MX in the targeted M reservoir bed and drilling the lateral section. The major geosteering technologies used are the at-bit resistivity and azimuthal propagation resistivity, which provides geostopping capability, reservoir bed boundary mapping and accurate distance to bed boundary calculation. These technologies helped in keeping the wellbore within the hydrocarborn unit of the M reservoir. Performing formation pressure testing in realtime, the team was able to carry out a reservoir gradient analysis which helped with reservoir fluid identification, fluid contact determination, and connectivity of hydrocarbon zones before drilling was concluded.
Well-MX is a horizontal well located in the Mirum field of the Niger Delta Basin, offshore Nigeria. The well was drilled to target the deep multi-lobed M reservoir to a total hole depth of 11,307ft MD. By using Well-MX as a case study, this paper discusses how the combination of reservoir navigation service and real-time formation pressure sampling helped meet drilling objectives for this well. Some of the challenges encountered includes vertical seismic interpretation uncertainty, poor reservoir quality along the drain hole section, change in depth of oil to water contact and undulating bed boundaries. Other challenges and decisions taken to successfully geosteer the well will be reviewed in this paper.