Helping organize Education Day at the 2006 Abu Dhabi Intl. Petroleum Exhibition and Conference (ADIPEC), which took place in early November, was marvelous. Approximately 67 students from 24 institutes throughout the Middle East were selected by the conference organizing committee to meet with final-year students and young professionals from different engineering and cultural backgrounds and to work together during Education Day. They also had the opportunity to attend ADIPEC, which had excellent speakers and exhibits. Such an experience was very rewarding to both the students and young professionals.
The idea started at a November 2005 Middle East Young Professionals (YPs) council meeting in Doha, Qatar: holding the first Middle East YP workshop. With excellent teamwork and organization, the workshop took place in Abu Dhabi from 31 October to 3 November. The event included discussion of the role of YPs in the future of the oil and gas industry and featured interactive sessions on technology and innovation; leadership; career development; health, safety, and the environment (HSE); and diversity and inclusiveness. Attendees came from Bahrain, Egypt, France, India, Oman, Saudi Arabia, United Arab Emirates, and the U.K. The workshop began with remarks by 2007 SPE President Abdul Jaleel Al-Khalifa, who emphasized how the industry should prepare young professionals to take on the challenges of today and tomorrow. Attendees agreed that they need to always try to improve their skills, be proactive, understand and apply the vision of their organizations, and implement new ideas to directly help their business units.
This paper discusses the re-construction of the long-term development plan for an offshore giantfield located in Abu Dhabi with the aim to mitigate the rising challenges in the maturing field. The primary objective is to understand the reservoir behavior in terms of fluid movement incorporating the learning from the vast history while correlating with the geological features.
The field has been divided into segments based on multiple factors considering the static properties such as facies distribution, diagenesis, faults, and fractures while incorporating the dynamic behaviors including pressure trends and fluid movements.
On further analysis, various trends have been identified relating these static and dynamic behaviors. The production mechanism for each of the reservoirs and the subsequent sub reservoirs were analyzed with the help of Chan plots, Hall plots and Lorentz plots which distinctly revealed trends that further helped to classify the wells into different production categories.
Using the above methodology the field has been categorized in segments and color coded to indicate areas of different ranking. The green zone indicates area of best interest which currently has strong pressure support and wells can be planned immediately. The wells in this area are expected to produce with a low risk of water and gas. The yellow zone indicates areas of caution where special wells including smart wells maybe required to sustain production. This area showed relatively lower pressure support owing the location of the water injectors and the degraded facies quality between the injectors and the producers. The red zone highlights areas which are relatively mature compared to the neighboring zones and will require new development philosophy to improve the recovery. The findings from this study were used as the basis for a reservoir simulation study using a history matched model, to plan future activities and improve the field recovery.
This study involved an in-depth analysis incorporating the latest findings with respect to the static and dynamic properties of the reservoir. This has helped to classify the reservoir based on the development needs and will play a critical role in designing the future strategies in less time.
Bhushan, Yatindra (ADNOC Onshore) | Ali Al Seiari, Reem (ADNOC Onshore) | Igogo, Arit (ADNOC Onshore) | Hashrat Khan, Sara (ADNOC Onshore) | Al Mazrouei, Suhaila (ADNOC Onshore) | Al Raeesi, Muna (ADNOC Onshore) | Al Tenaiji, Aamna (ADNOC Onshore)
A reservoir simulation study has been performed to assess the enhanced oil recovery benefits for a proposed pilot on Simultaneous Injection of Miscible Gas (CO2) and Polymer (SIMGAP) in a giant carbonate reservoir (B) in Abu Dhabi. The model has been used to carry out uncertainty analysis for various input parameters and analyze their impact on pilot performance. The paper discusses the uncertainty analysis in detail.
Reservoir-B consists of B_Upper and B_Lower layers which are in full hydrodynamic equilibrium. However, in the southern and western parts of the reservoir, the B_Upper layer has permeabilities that are one to two orders of magnitude higher than the B_Lower layer. The reservoir is on plateau production under waterflooding, however, it is observed that there is water override in B_Upper. The B_Upper layer is being waterflooded very efficiently, while the B_Lower layer remains largely unflooded and forms the key target for enhanced oil recovery (EOR).
The proposed SIMGAP pilot plans to inject polymer into the B_Upper layer and CO2 into the B_Lower layer with producers in the B_Lower layer. The pilot will utilize a line drive pattern at 250m spacing using 3000 ft horizontal wells. There will be two central horizontal injectors (one in B_Upper and the other in B_Lower) and two horizontal producers (one on either side of the central injectors).
Pilot uncertainty analysis cases have been run by varying different parameters that could impact the pilot performance. The parameters that have been varied are polymer viscosity, polymer adsorption, residual resistance factor, thermal stability of polymer, residual oil to miscible flooding (Sorm), residual oil to water flooding (Sorw), Krw end point, high perm streaks, fracture possibility and extension to B_Upper or B_Lower layers, three phase oil relative permeability models, maximum trapped gas saturation, dense zone permeability and pore volume uncertainty. In addition, a grid sensitivity study was undertaken to test the sensitivity of the process to varying levels of dispersion. The results suggest that the key uncertainties which have impact on recovery are polymer viscosity, polymer adsorption, residual oil saturation to water and CO2, presence of high perm streaks and maximum trapped gas saturation values. Vertical observation wells located between the injector and producer wells (equivalent to 0.3 to 0.4 PV of CO2 injection in B_Lower), will be used to confirm whether the SIMGAP process has been successful in containing CO2 in the B_Lower layer and thereby suppressing crossflow.
This work presents a new open access carbonate reservoir case study that uniquely considers the major uncertainties inherent to carbonate reservoirs using one of the most prolific aggradational parasequence carbonate formation set in the U.A.E; the Late Barremian Upper Kharaib Mb. as an analogue. The ensemble considers a range of interpretational scenarios and geomodelling techniques to capture the main components of its reservoir architectures, stratal geometries, facies, pore systems, diagenetic overprints and wettability variations across its platform-to-basin profile.
Fully anonymized data from 43 wells across 22 fields in the Bab Basin, U.A.E from different geo-depositional positions and height above FWL’s (specified to capture multiple structural positions) within an area of 36,000 km2 was used. The data comprises of a full suite of open hole logs and core data which has been anonymized, rescaled, repositioned and structurally deformed; FWL’s were normalized and the entire model was placed in a unique coordinate system. Our petrophysical model captures the geological setting and reservoir heterogeneities of selected fields but now at a manageable scale.
The novelty of this work has been to create semi-synthetic
Reservoir A is being developed in early and interim phases in order to gather static & dynamic data to minimize the risk associated to subsurface uncertainties. In early and interim phases, only production is taking places. During full field, water injection scheme will be implemented using mainly 5-spot pattern. It is very crucial to measure the subsurface uncertainties and their impact on the reservoir development. For this purpose, the uncertainty parameters are identified and their ranges are selected based on the current well performances during probabilistic History matching (PHM) phase. In full field runs, the uncertain subsurface parameters are quantified to prioritize the future reservoir monitoring and data gathering plans. Note that wells are equipped with the permanent downhole pressure gauges.
Reservoir A is one of the major reservoirs of a green-field located offshore Abu Dhabi and is being developed with a 5-spot water injection pattern. The producers and water injectors are horizontal wells which are drilled across different flow unit within the reservoir. The reservoir properties are variable across all the flow units, which may results in a non-uniform water front. Being a green field, there are more uncertainties as compared to the brown field. More than three years production & pressure data is available which is used in this uncertainty study. This production data is mainly used to achieve the probabilistic History match on well-wise basis. In this uncertainty study, previous HM parameters are removed. However, based on previous history matching learnings, the subsurface uncertain parameters ranges are selected for this probabilistic History match phase. The criteria for filtering the valid runs during this phase are set to be ±150 Psi compared to the actual downhole pressure readings. In case of decreasing this filtering range to 75 Psi, results in reduction in the reserve range in P90 to P10. Based on ±150 Psi principle, the subsurface parameter ranges are furthered reformed for full field uncertainty study/run. The industry standard workflow is followed to quantify the subsurface parameters during this phase. In this study, we used the Permeability modifiers based on RRT, Faults transmisibilities, Relative Perm curves (based on SCAL data), Kv/Kh ratio (from PTA), etc. as uncertain parameters. The impact of each parameter is measured and quantified with respect to plateau and total reserves.
Enhanced oil recovery ("EOR") by means of CO2 injection has become a globally-used method of increasing oil recovery. Interest in the UAE has increased in recent years due to the proven effectiveness of the process, and due also to government plans to initiate a world-class CO2 capture campaign.
EOR by means of CO2 injection is associated with many challenges. The majority of EOR projects are conducted in onshore fields since offshore EOR experience is limited by technical and operational challenges, as well as by higher economic hurdles. A larger resource base is required to justify an offshore EOR project than a project that is located onshore. Apart from that, the decision to embark on a CO2 injection project is often complicated by the lack of multidisciplinary integration. Uncertainty analysis should be included in the evaluation since it is critical to understanding pilot objectives, identifying model limitations, proper scaling of results from the pilot area to the field, and managing expectations. The economics of the proposed project are strongly dependent on proper baseline definition – possible only by means of advanced methods of reservoir characterization – and by state-of-the-art methods of dynamic reservoir simulation using a fully-compositional model and robust equations of state to characterize the process physics.
The oilfield discussed in this paper is a digitalmulti-reservoir field being developed by horizontal and highly-deviated wells equipped by inflow control devices (ICD). Primary depletion will be augmented by reservoir-specific water injection and hydrocarbon gas injection. Field characterization is being done based on data from comprehensive open- and cased-hole log suites, seismic data, MDT runs, PTA, and an array of SCAL and PVT tests necessary to fully describe the process physics.
The purpose of this paper is to describe the workflow and methods used to design, and estimate the efficiency of a CO2 injection project for a giant carbonate reservoir complex in the offshore area of the UAE. Recommendations for pilot project and surveillance program designs based on best practices and lessons learned from prior projects, developed to overcome the challenges described above, are discussed.
Full field development of the Upper Jurassic carbonates, offshore Abu Dhabi is exceedingly challenging. The heterogeneous texture, complicated pore systems and intensive lithology changes all mark the regressive cycles of sedimentation. Such complicated characteristics obscure formation evaluation of these formations. Advanced well logging tools and interpretation methodologies are implemented to minimize the petrophysical uncertainties to qualify the products as field development critical elements. This case study highlights a newly applied NMR log interpretation approach. The results help to understand the complex pore system in a tight carbonate layer, along a horizontal drain drilled close to the oil-water contact.
NMR log data was acquired in real-time while drilling simultaneously with Gamma Ray, Resistivity and Image Logs. Earlier field studies recommended swapping standard T2 free fluid relaxation cutoff values by actual laboratory NMR measurements for a higher precision suitable for the reservoir texture heterogeneity, the study itself supported the application of higher cutoff values to better discriminate the free fluid in well-connected macro pores from the irreducible which will have a direct impact on the computed permeability.
In this case study, a variable free-fluid T2 cutoff was firstly implemented based on arbitrary estimations to match the computed Coates permeability to the offset core values. Free-fluid, irreducible fluids were sequentially computed. A unique NMR-Gamma Inversion (NMR-GI) workflow is further utilized as a mathematically defined approach to process the raw data using probabilistic functions. The result is a more precise pore size distribution, coherent with the geological variations. NMR Capillary pressure was computed.
The complex formation texture could be accurately tracked for thousands of feet drilled along the horizontal drain. After validation with offset core, the NMR-GI interpretation was combined with, Archie saturation and Image log analysis for a conclusive assessment. Hydraulic flow units were combined. Successful completion design and production zone selection articulated on the defined open hole log interpretation.
NMR while drilling logging and the applied (NMR-GI) methodology prove to be leading tools to assist in resolving carbonate reservoir complexities. Not only that they help to understand the pore system characteristics, but they effectively support well placement, completion and production.
Downhole control devices are being widely implemented in fields globally; and, because of the costs involved in their implementation, a robust reservoir performance forecast is necessary. A prerequisite to a sound reservoir development plan is to have a robust history-matched reservoir simulation model. This study involves use of a downhole inflow control device (ICD) well configuration in the reservoir simulation model to perform history matching of a green-field offshore Abu Dhabi. The results of this approach are compared to the results from traditional approaches. The scope of this study is to examine the differences in both history match approaches.
Reservoir A is one of the major reservoirs of a green-field located offshore Abu Dhabi, and is being developed with a five-spot water injection pattern. The producers and water injectors are horizontal wells, which are drilled across different flow units within the reservoir. Because the reservoir is heterogeneous across all the flow units, the injection pattern results in a non-uniform water front. The conventional approach to history matching the well performance is to implement a positive skin factor across the well completions to mimic the effect of the inflow control devices (ICDs) installed in the well: increasing the pressure drop (ΔP) between the formation and the well tubing. In this study, the actual downhole configuration was prepared using well-completion analysis software, followed by use of a next-generation reservoir simulator to run the full field reservoir model for the history matching period.
As the field is being developed on the principles of digital concept, continuous high-frequency downhole pressure data is available in flowing as well as shut-in conditions. The use of this data, coupled with direct modeling of the ICDs in the simulation model, resulted in a significant improvement in the reliability of the history match, as compared to traditional approaches.
This study compares two history matching approaches for fields with wells completed with downhole control devices. The core purpose of this study is to integrate the principles of the digital oil field with conventional history matching techniques, with the ultimate goal of improving the history match.
Field presented here is located in offshore Abu Dhabi, consisting of multi-stacked reservoirs with different fluid and reservoir properties. In this paper, field development plan of one of reservoir has been presented which was initially planned to be developed with pattern water injection by more than 50 horizontal wells penetrating all the ten oil bearing layers from 9 well head towers. Reservoir consists of under-saturated oil with low gas-oil ratio and low bubble point. Initial 2 years of production was considered as Early Production Scheme (EPS period), during which significant amount of early production data consisting of downhole pressure measurement, time-lapse MDT, vertical interference data, PLT have been collected. Based on EPS data simulation model has been updated. Simulation fits well with the observed pressure gauge and time-lapse MDT data. Updated model gives good prediction for a year of blind test data (including saturation, MDT and porosity) collected from different wells several kilometers away from current development area reflecting a high level of confidence in areal and vertical connectivity representation. Considering other reservoir uncertainties different Development plans have been screened using updated model in order to improve recovery factor and economics. Based on development plan screening study, optimized development option has been chosen for Full Field Development.