Menon, Pradeep (ADNOC Upstream) | Anurag, Atul (ADNOC Offshore) | Mills, Carey (ADNOC Upstream) | Basioni, Mahmoud (ADNOC Upstream) | Steiner, Stefan (ADNOC Upstream) | AlBlooshi, Mohammed (ADNOC Upstream) | Dasgupta, Suvodip (Schlumberger) | Guerra, Julian (Schlumberger) | Shasmal, Sudipan (Schlumberger) | Adil Suliman Salim, Israa (Schlumberger)
The Khuff Formation is a Permo-Triassic aged carbonate unit which reservoirs a highly economic gas resource in several countries within the Middle East. The appraisal and development of Khuff Formation tight gas resources is the subject of increased focus in the offshore UAE. This case study focuses on the appraisal of a particular field in offshore Abu Dhabi and summarizes how the understanding of this complex reservoir has evolved over time.
The oldest well penetrating the Khuff Formation in this field was drilled almost 3 decades ago. This well tested gas within the Upper Khuff however appraisal of this resource had to wait until 2017-18 when two appraisal wells were drilled on the discovery. These appraisal wells included a complete suite of wireline logs, image log data, formation pressure measurements and well tests to give a clearer picture of the formation and fluid saturations. Subsequent to the drilling of the recent appraisal wells an integrated study was completed integrating all the processed and advanced answer products in order to determine the key elements controlling gas productivity. This knowledge were subsequently applied to optimise a well drilled and production tested in late 2018.
Understanding the production behavior of the Khuff Formation reservoirs intervals has been one of the most critical factors behind the decision to develop this complex reservoir. Certain key answer products are considered critical for identification of completion intervals. These products include; sonic imaging (looking for fractures away from the wellbore), advanced textural analysis from borehole images (porosity classification) and critically stressed fracture analysis from geomechanics. This study led to the conclusion that critically stressed fractures and/or connected pores from images are the best indicators of high gas flow potential, while this flow can become exponentially higher when fractures at the wellbore connect to fractures away from the wellbore. This workflow has now been applied to the most recently drilled well and to other Khuff Formation appraisal projects across the off shore of Abu Dhabi.
This is an illustration of how in-depth analysis of all the acquired data in an integrated manner can help in understanding a complex reservoir and lead to better decision-making for the future wells and offset appraisal projects. Lessons are hidden in both success and failure and as long as these lessons are analyzed properly, they can lead to long-term success.
Reservoir management guidelines are an enabler of, production sustainability, assurance to reservoir health and high ultimate recovery. Monitoring the compliance of the field production against the set of reservoir management guidelines is one of the key processes for ADNOC, being a governing body of major U.A.E. hydrocarbon producing fields.
With the business need to ramp up production, field maturation, and the associated operational challenges, it is critical for ADNOC to effectively monitor and regulate its field production plans to assure the long-term production sustainability. In this regard, ADNOC has developed a robust framework that is implemented through an automated analytics platform that enables different ADNOC technical teams to effectively monitor and report the compliance status of each hydrocarbon barrel from produced from ADNOC assets. The paper highlights the features of the workflow implemented, the management of change strategy and the business value created.
The automated process allows the consolidation of a variety of well, reservoir and field-level data. The analytical platform enables integrated analysis, KPI calculation and interactive visualization. The framework assesses the compliance based on three governing parameters: well technical rate, gas-oil ratio (GOR), and bottom hole flowing pressure. The compliance analysis is carried out on a monthly basis where the monthly back allocated production data for each well is compared with the set of operating guidelines in an automated data analytics and visualization environment. A pragmatic compliance tolerance is considered in the calculations to accommodate the measurement inaccuracies, as well as the operational limitations while allowing flexibility to exclude nonconformity with valid reasons.
The overall process is governed through an automated business process management (BPM) platform, which seamlessly regulates the predefined subroutines among different stakeholders to report and track different corrective actions in a timely manner.
The framework implementation has strengthened the overall compliance governance process; and has been instrumental to properly manage asset production capacity in a systematic manner. This has subsequently enabled the preparation of a prompt action plan and has improved the operating efficiency of more than 3% within the first six months of implementation, through restoring, compensating and increasing the effective capacity of overall ADNOC Production.
The approach has demonstrated great value both in terms of process alignment, as well as from the production assurance standpoint at a country level, and allows the organization to have an established system, which provides: Consistent compliance monitoring standards Minimal subjectivity Complete process governance Quick turnaround time Auditable history
Consistent compliance monitoring standards
Complete process governance
Quick turnaround time
The aim of this paper is to publish a stepwise guide for any operators who might be interested to adopt and implement a similar approach to assure the long-term production sustainability and health of their assets.
Noei, Emad Ghaleh (Dept. of Geomatics Engineering University of Calgary, Canada) | Dettmer, Jan (Dept. of Geoscience, University of Calgary, Canada) | Ali, Mohammed (Dept. of Earth Sciences, Khalifa University, UAE) | Lee, Gyoo Ho (Korea Gas Corporation, Korea) | Kim, Jeong Woo (Dept. of Geomatics Engineering University of Calgary, Canada)
This work investigates nonlinear inversion of gravity data to infer Infracambrian Hormuz salt structures offshore Abu Dhabi, UAE. A Bayesian approach with a trans-dimensional parametrization of the subsurface is applied that does not require regularization, resulting in more objective inversion results. The trans-dimensional parametrizations discretize the subsurface structure including the salt dome by an irregular grid of Voronoi cells. Both the number of cells and the cell coordinates are unknown parameters estimated from gravity data. The density contrast of the salt structures is assumed as known. The solution in Bayesian inversion is given by a large ensemble of parameter sets. Here, the trans-dimensional ensemble is obtained with the reversible-jump Markov chain Monte Carlo (rjMCMC) algorithm. Residual errors are parametrized by a full covariance matrix, which is estimated and updated as part of an iterative inversion scheme. Efficient rjMCMC sampling is achieved with parallel tempering. Inversion of airborne gravity anomalies illustrates well-defined Infracambrian Hormuz salt structures offshore Abu Dhabi, where the irregular grid spatially adapts to the data information and without the need to impose explicit regularization or fixed grids. Uncertainty estimates highlight salt dome extent. This study provides new insight into the existence and shape of oil reservoirs associated with the underlying salt structures.
Taher, Ahmed (Abu Dhabi National Oil Company) | Al Hanaee, Ahmed (Abu Dhabi National Oil Company) | Frsnco, Bernardo (Abu Dhabi National Oil Company) | Chitrao, Amogh (Abu Dhabi National Oil Company) | Abdelaal, Atef (Abu Dhabi National Oil Company) | Popa, Desdemona (Abu Dhabi National Oil Company)
Recently there has been a growing interest in gas exploration, much of this focus has been directed toward thermogenic gas derived from cracking kerogen in the highly mature kitchens. However, a significant proportion of the global gas reserve is not thermogenic but of bacterial origin (
The recent exploration wells drilled in the northeast onshore Abu Dhabi showed elevated total gas readings during the drilling of the Gachsaran formation. Consequently, mud-weight was increased to control the gas flow. In addition, the recorded wireline logs indicate the presence of relatively high hydrocarbon saturations in several high porous zones of Gachsaran and Asmari formations.
To assess the productivity and commerciality of the Biogenic gas potential in Abu Dhabi, several exploration wells are planned to be drilled before the end of 2019. The positive results of these wells will open the door for a new era of sweet gas exploration activities in Abu Dhabi and its surrounding areas. The primary gas reservoirs are thin carbonate and clastics layers in the Gachsaran Formation at a depth that ranges between 1600-5200 feet below sea level.
Organic carbon isotopes, Rock Eval analysis, TOC log data and gas shows analysis indicated that the methane gas found in the Gachsaran Formation is of a biogenic origin and sourced mainly from the organic-rich argillaceous limestone of the Middle Gachsaran.
Gachsaran formation is comprised of alternating thin layers of anhydrite, limestone, marl and shale sediments in addition to the presence of salt layers in the lower part. This mixed lithology resulted in the reservoirs property deterioration in particular by shale and anhydrite nodules cementation.
The biogenic basin areal extent, significant thickness of the Gachsaran in this basin and the organic richness distribution, conclude possible generation of a huge volume of biogenic gas in northeast onshore Abu Dhabi. However, additional work is required to estimate the volume of gas that is accumulated and that can be produced from the Gachsaran and Asmari formations.
Torres, Kevin (Abu Dhabi National Oil Company ADNOC Onshore) | Pinto, Ruben (Abu Dhabi National Oil Company ADNOC Onshore) | Romero, Liliana (Abu Dhabi National Oil Company ADNOC Onshore) | Ortiz, Jhon (Abu Dhabi National Oil Company ADNOC Onshore) | Khoori, Suaad (Abu Dhabi National Oil Company ADNOC Onshore) | Al Khaabi, Jameela (Abu Dhabi National Oil Company ADNOC Onshore) | Prahawinarto, Bambang (Abu Dhabi National Oil Company ADNOC Onshore) | Al Madani, Noura (Abu Dhabi National Oil Company ADNOC Onshore) | Al Ameri, Fatema (Abu Dhabi National Oil Company ADNOC Onshore) | Al Rawahi, Ali (Abu Dhabi National Oil Company ADNOC Onshore)
During the last decade, some problems have appeared and being affecting the oil production of the mature giant oil field such as: flow boundaries, by pass zones, fractures, etc. hence, the characterization of the reservoir by the integration of static and dynamic data acquired along the field life is required. The new generation of static model is justified in the need to involve the lessons learnt from the previous static/ dynamic models with the incorporation of the recent studies and well data. The aim of this article is to integrate the structural seismic interpretation and results of pressure transient analysis obtained from well test, such as distance to potential flow boundaries, average permeability, among others, into the workflow of the new geological static model, through the validation with the conceptual geological understanding of the reservoir. Such workflow not only considers different sources for the reservoir characterization but also reduce the alternative solutions of the well test data to the best-fit solution for the integration. In a typical geological modeling workflow, structural framework is built first, based on the zones definition that include well information, well log data, structural seismic interpretation and the stratigraphic characterization that allow capturing the vertical heterogeneity. Subsequently, the sedimentary-stratigraphic architecture is used as main constrain together with geostatistical methods to distribute the petrophysical properties for each zones. The well test results independently are a punctual dynamic response of the reservoir in a portion of the time and within a certain tested area around the well. However, the integration with the conceptual geological model can resolve the uncertainty that alone cannot respond enable a more robust interpretation of main reservoir heterogeneities. The study proposes the inclusion of the well test data to support and validate, firstly the structural connectivity of the zones through the well test interpretation (validation of faults, dual porosity zones, dense zones, etc.), and secondly calibrate the permeability model with additional dataset than only from cores, which, even though derived from dynamic data, are incorporated in the static model workflow.
Halokinesis has strongly stimuluses the Abu Dhabi petroleum system. During the Late Precambrian, the basement terranes of the Arabian and adjoining plates were fused along the northeastern margin of the African Gondwanaland plate. This phase was followed by continental rifting and intra-continental extension. The Arabian Infracambrian extensional system established rifted salt basins in the Zagros region, South Oman and in the Arabian Gulf. The Hormuz salt in these areas contains basalt and rhyolite, suggesting tectonic extension at this time. The Zagros thrust fault and Dibba transform fault define the current limits of the Hormuz Complex of the Arabian Gulf. As a passive margin during Paleozoic time, the Arabian plate accumulated a continentally influenced shallow marine sequence characterized by interbedded siltstones, sandstones, shales and carbonates sediments. The Late Ordovician-Early Silurian glaciation interrupted the Paleozoic deposition by lowering sea level in the Late Silurian and Late Carboniferous-Early Permian glaciation.
Salt movement was started an extensional phase in Permo-Jurassic with the Neo-Tethys opening and basement faults reactivation. Followed by Cretaceous compression stress due to Afro-Arabian Plate movement. The third phase happened by Late Cretaceous with the closing of the Neo-Tethys. The salt was finally pierced to the surface by Mid Tertiary compression stress forces accompanied with Oman thrusting and Zagros folding. Since Miocene uplift, the salt movement extended until present day onwards. Previously, the pierced salt was considered stacked, but subsidence measurements indicating salt is still moving in some islands reaching about 2cm per year.
This paper uses 3D seismic, core data and outcrops investigations to assess the geometry, kinematics, and the halokinetic phases that stimuluses the hydrocarbon exploration targets. The paper revisited the flowage phases of the salt in Abu Dhabi, investigated the accompanying fault geometries and relate this to the structural styles. The diapiric anticlines forming during salt movement phases forming domal structures with radial faults. Contradicting what is known, the Miocene-recent strata are tilted indicating the continuation of the salt movement. The Hormuz salt is characterized by a regionally consistent stratigraphy, formed of evaporites interbedded with clastic and carbonate sediments with dolomite intervals and vein intrusions of volcanic rocks.
Interpreted faults were categorized into three families, Type I comprising domal radial faults, Type II representing faults triggered salt movements and Type III describing salt movements triggered faults. The first type is characterizing itself by its location relative to the crystal parts of the domes. The relatively low overburden pressure at the crest of the diapir and the original high dip angles of these fault planes favor salt intrusions near the diapir crest. Depending on the salt movement phases, the generated cycles of these faults, are characterized by different dips and areas of extension, while the other two categories can be differentiated as well. At the time of salt movement initiation, these faults were incipiently intruded by salt for relieving the intense internal overpressure in the salt body. These pressures are due to the compression forces associated with the salt movement, the buoyancy effects compensating the density difference between salt and overlying sediments and the tectonic compression forces. The latter is the reasonable mechanisms that allow salt penetration along fault planes and bedding planes.
This paper provides evidences that salt movements impact the petroleum system, especially traps, as if the salt movement preceding the hydrocarbon migration, this leads to faults sealing and the reverse is also applied.
Hydrocarbon belt is as a tectonic zone along which most hydrocarbons accumulate. Five major hydrocarbon belts are identified on the Arabian scale that are consistent; possess similar trends and geologic history. These are the NE-SW trend of the onshore Abu Dhabi fields, the N-S trend of Saudi Arabia, Kuwait and southern Iraq, the NW-SE trend is represented by Southern-Central Iraq, and the E-W trend in northern Iraq, Syria and Turkey. The fifth category includes fields related to salt doming events, which are not characterized by a systematic trend but can be restricted to specific areas where salt movements played a major role. Understanding these belts and their geologic concepts can predict new exploration potentials between or within the existing fields.
The extent to which the stress state has influenced hydrocarbon distribution through geologic time can be directly seen on the fields maps. An important element on the existence of the hydrocarbon accumulation belts are that almost all fields in the Arabian plate and the foreland basin have not been obliterated by subduction. The continental collision of the Arabian plate with Eurasian plate produced high-pressure/low-temperature structural belts forming hydrocarbon traps resulting from deformation. This lead the hydrocarbon to move from high-pressure to low-pressure zones, leading the hydrocarbon migration and entrapment process towards low-pressure regions.
Many wells drilled with direct measurements of in situ stress allows the estimation of the direction of the stress vectors. Using the local stress orientations in Abu Dhabi while linking this to tectonic events and combining with the Arabian stress trajectories fed the methodology and workflow presented in this paper.
The results show that the stresses affecting Abu Dhabi can be categoriesed into: (1) The differential stress generating detectable azimuthal variations due depth; (2) The pre-inherited stress trajectories; and (3) the stresses related to the wrench fault segments. The pressure associated with these stress trajectories is the main driver for the hydrocarbon migration and filling of the traps. Applying these stress trajectories with the variances in the state of stress of different stratigraphic layers, enables understanding of where the hydrocarbon is trapped.
Prediction of the migration trajectories is a very useful tool for exploration, specifically for the identification of new leads and plays, as well as for constructing new theories on the equilibration of the fluid levels and observations of residual oil below the current established free water levels.
Kang, Jeonggil (Al Dhafra Petroleum Operation Company) | Eriavbe, Francis (Al Dhafra Petroleum Operation Company) | Girinathan, Sajith (Al Dhafra Petroleum Operation Company) | Mohamed, Alyazia (Al Dhafra Petroleum Operation Company) | Doucette, Neil (Al Dhafra Petroleum Operation Company) | Almehsin, Khalil (Al Dhafra Petroleum Operation Company) | Ali Alloghani, Jasim (Al Dhafra Petroleum Operation Company) | Ali Al-Ali, Abdulla (Al Dhafra Petroleum Operation Company) | Ahmed Al Katheeri, Faaeza (Al Dhafra Petroleum Operation Company) | Bhatt, Pranjal (Baker Hughes, a GE Company) | Franquet, Javier (Baker Hughes, a GE Company) | Zhunussova, Gulzira (Baker Hughes, a GE Company) | Uluyuz, Sila (Baker Hughes, a GE Company)
Several challenges are associated with the characterization of organic rich unconventional plays, most significantly with the identification of sweet spots for optimum placement of horizontal wells, estimation of producible hydrocarbons and subsequent stimulation design. This paper presents the petrophysics and geomechanics integration approach from the X Formation and the important factors for the identification of sweet spots.
The case study concentrates on the X Formation that consists of a succession of argillaceous limestone, mostly fine grained packstones and wackestones together with subordinate calcareous shales in the lower part. The complex carbonate lithology and fabric combined with low porosity and the requirement to evaluate total organic carbon presents a challenge to conventional logs and evaluation of them. Amid all the rock properties, the low permeability and productivity dictate the requirement to stimulate the wells effectively. Detailed integration of advanced and conventional log data, core data, mud logs and geomechanical analysis plays a critical role in the evaluation and development of these organic rich unconventional reservoirs. Extensive data gathering was done with wireline logging suite, which covered Resistivitiy/Density/Neutron/Spectral GR- Acoustic logs – Resistivity & Acoustic Images – Dielectric- NMR - Advanced Elemental Spectroscopy technologies and microfrac tests to characterize the hydrocarbon potential, sweet spots and in-situ stress contrast within the organic rich X Formation. The azimuthal and transverse acoustic anisotropies were obtained from X-dipole data to fully characterize the elastic properties of the formation. The static elastic properties were obtained using empirical core correlations as triaxial core tests were not available at the time of the study. The stress profile was calibrated against straddle packer microfrac tests to identify intervals with stress contrast for proper hydraulic fracturing interval selection.
The integration of conventional and advanced logs enabled the accurate evaluation of total organic carbon (TOC), petrophysical volumes, and sweet spot selection. The advanced elemental spectroscopy data provided the mineralogy, amount of carbon presence in the rock, and consequently the associated organic carbon within the X Formation. The NMR reservoir characterization provided lithology independent total porosity. The difference between the NMR and density porosities provides additional information about organic matter. NMR data was utilized in this case study to identify and differentiate the organic matter and hydrocarbon presence within the X Formation.
Acoustic and image logs provided the geomechanical properties that enable selection of the best intervals for microfrac stress measurement and proper fracture containment modeling. Geomechanical workflow allowed identification of intervals with a good stress contrast in X formation. The core data and stress measurements are recommended for the accurate calibration of the stress profiles and hydraulic fracture propagation modeling.
The extensive data integration work presented in this single-well study within X Fomation, is a key factor for any organic rich unconventional reservoir characterization that integrated geology, petrophysics, mineralogy, and geomechanics for sweet spot identification within tight oil carbonate reservoirs.
Drilling deep exploration wells to Pre-Khuff formations requires considerable investment and therefore data gathering through logs and cores should be of highest quality to maximize value of information. The abrasive nature combined with high downhole temperatures and bit sticking present a uniquely hostile environment. In this paper, we discuss challenges in data acquisition and propose best practices for logging and coring programs tailored for Pre-Khuff exploration targets.
The oldest Pre-Khuff stratigraphic unit penetrated offshore is Silurian Qusaiba equivalent. Apart from Permo-carboniferous Unayzah, the other stratigraphic units encountered in Abu Dhabi Offshore are Permian Basal Khuff Clastics (BKC), Early Carboniferous Berwath, Silurian Tawil /Sharawra Formations. In recent years, a number of deep exploration wells penetrated Pre-Khuff in various offshore fields, often under challenging high temperature and high pressure conditions. Considering extensive data gathering programs, this includes mud logging, LWD, wireline logging, and core extraction followed by detailed core analysis.
Log data acquired through wireline is frequently impaired by wash outs and bad hole conditions, hence posing a challenge to assess rock properties reliably. Cores were successfully acquired as whole core and sidewall core and extensive core analysis programs were conducted.
The key objectives for data gathering in Pre-Khuff are lithostratigraphy, sedimentology and age dating, petrophysical properties and prove hydrocarbon presence as well as geomechanical properties for hydraulic fracturing of the formation for subsequent well testing operations.
Palynological analysis at well site is important for age determination. Correlation of mud logging results with open hole logs and Borehole image logs proved essential to determine hydrocarbon presence. The complex lithology mix is best resolved with elemental spectroscopy logging. LWD log acquisition is preferred over wireline because of a reduced risk of stick and pull and minimum invasion. However, some useful measurements such as Dielectric log are currently only available through wireline and industry should develop this tool for LWD. NMR tools generally cannot cope with the high temperature environment. Hence, service industry is encouraged to provide higher spec NMR tools. Due to low matrix permeability, core analysis for crushed rock or retort methods are preferred to obtain permeability measurements through pulse decay and pressure decay methods.
Recommendations are given for optimal data gathering to ensure maximum value of information and best possible data quality. Logging operations should be a combination of Logging-While –Drilling and Wireline operations. Core acquisition will have to exclude BKC (Basal Khuff Clastic) to limit the risk of core jamming. A typical core analysis program to assess petrophysical and geomechanical properties for Pre-Khuff is proposed, leading to a successful risk assessment prior to hydraulic fracturing of the formation. Further lithostratigraphic and age-determination techniques are included in the scope.
Al Kindi, Arwa (ADNOC Onshore) | Al Tandi, Ahmed (ADNOC Upstream) | Abdou, Medhat (ADNOC Upstream) | Xu, Siqing (ADNOC Upstream) | Kumar, Heer (ADNOC Upstream) | Zivanov, Drago (ADNOC Upstream) | Loobari, Sultan (Al Yasat Petroleum) | Al Mazrouei, Nadia (ADNOC Onshore)
Every market intelligence on energy these days converges on a unanimous view that despite the push on developing alternative energies, fossil fuel will continue to play a pivotal role in world energy supply. The competition between fossil fuel and alternative energies is a new reality. To maintain a competitive edge, sustainability and favorable economic returns shape the UAE's approach to future oil developments.
UAE oil production is analyzed to reflect the critical importance of production contribution to the world and within the MENA region. Two published international field development cases are analyzed, focusing on the impact of aggressive approach on production sustainability, potential challenges and costs in developing the remaining bypassed oil. By using typical Abu Dhabi reservoir field data, various development scenarios are simulated demonstrating potential impact on production sustainability, ultimate recovery and economical value for the country.
Today National Oil Companies (NOC's) have an advantage as they own and control more than 90% of the total world oil and gas reserves. In contrast, the top six largest International Oil Companies (IOC's) combined control less than 5% of the total. Clearly, IOC's will face challenges in reserves replacement. Although there are different factors affecting reserves replacement rate, one of the key to enhanced economic reserves position for IOC's is field depletion strategy.
An ideal field depletion strategy would see production at lower depletion rates to ensure efficient reservoir drainage for maximizing recovery. An aggressive field depletion strategy can potentially generate faster monetary returns through higher production, but may create by- passed oil that would be difficult and costly to extract. An optimal field depletion strategy ensures sustainable development, maximizes ultimate recovery, and generates highest value return for the country and all stakeholders. A careful approach is required while deciding between these two different approaches, as the decision can have long lasting implications on corporates economic reserve position and global energy supply landscape. For example, a small improvement in ultimate recovery of existing reservoirs worldwide would add to and sustain affordable supplies, but a small reduction can potentially lead to supply shortages hindering world economic growth.
This paper presents the untold story of Abu Dhabi's Recovery Based Strategy. The aim is to perform a detailed analysis and comparison between two different development approaches, namely Aggressive Approach aiming to generate quick monetary value through high production (high depletion rates), and optimal / moderate field depletion strategy prioritizing sustainable development, and high ultimate recovery for all stakeholders.