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Collaborating Authors
Fryer, Vance I.
Challenges of Saturation Height Modeling in a Low Resistivity, Complex Carbonate Porosity System: The Impact of Microporosity in the Uwainat Formation, Bul Hanine Field, Offshore Qatar
Vizcarra, Edwin (Qatar Petroleum) | Kraishan, Ghazi (Schlumberger) | Hall, Jonathan (Qatar Petroleum) | Abdelouahab, Mariem (Schlumberger) | Fryer, Vance I. (Qatar Petroleum) | Chanpong, Robert
Abstract In complex and heterogeneous carbonate reservoirs, computing an accurate log derived water saturation (SW) where more than one pore type is present, poses a challenge for log analysts and geomodelers. Despite the application of a large number of log based techniques, log derived SW in these situations fails to compensate for the effects of microporosity because it does not accurately represent moveable hydrocarbon pore volume. Alternative techniques must be developed and implemented to reduce the uncertainty in hydrocarbon estimation and for use in dynamic simulation. Failing to account for the affects of microporosity can have a major impact on hydrocarbon reserve estimation because the capillary bound water contained in the microporosity can cause SW estimates using conventional open hole logs to be inaccurate and this can lead to inaccurate estimation of moveable hydrocarbons. Such errors lead to the possibility that some potentially productive intervals could be bypassed or confused as water productive, when in fact they produce dry oil in production tests. Furthermore, substantial errors in calculation of Original Oil in Place (OOIP) can also be made. We present the results of core based saturation height modeling for the Uwainat Member which has been applied to compensate for the dynamic effects of microporosity in simulation. Introduction The Uwainat Member is the main Mid-Jurassic carbonate reservoir in Bul Hanine (BH) Field, offshore Qatar. The Uwainat Member has an oil rim with an API gravity of approximately 37ยฐ, and fairly dry gas cap. The oil rim is about 140 ft thick and the gas cap column is approximately 260 ft. The oil saturation pressure at the Gas-Oil-Contact (GOC) is 4367 psia. Gas cap expansion provides the main energy for the reservoir flow. The Uwainat Member consists of a variety of carbonate rock types which are characterized by the occurrence of various pore types and complex pore geometry with varying proportions of microporosity. Complex pore size distributions encountered in carbonate rocks have a large impact on the fluid flow characteristics of reservoirs. Pervasive internal microporosity associated with micrite in packstone, wackestone, mudstone and even composite grainstone lithofacies affects the petrophysical properties of these rocks and challenges conventional modeling techniques. The presence of microporosity suppresses the resistivity response of induction and laterolog logging tools, leading to a low contrast in resistivity between water saturated and oil saturated rocks. Quantification of microporosity is critical in these lithotypes, to understand capillary behavior and why they appear to have such thick transition zones. In reservoirs such as the Uwainat at BH, primary drainage processes preferentially displace brine from pore network paths with the largest pore throat radii at the lowest elevations above the free water level (FWL). Microporosity remains brine saturated until much higher capillary pressures are reached. Internal micropores occur within fine grained particles which have high internal surface area. In microporosity, high surface area and the small pore size ensure that micropores remain water-wet at low capillary pressures. By contrast, the larger pores (macropores) are more susceptible to wettability alteration and can become oil-wet. In addition, drainage capillary pressure curves for rocks with a high proportion of microporosity tend to suggest or give the impression of a thick transition zone. This kind of apparent transition zone can be modeled by superposition of the capillary trends of two porosity systems, a micro and a macro system. Modeling the capillary pressure system in this way helps to explain the dynamic flow behavior of dry oil production in some of the Mid-Jurassic Uwainat intervals which have very low measured e-log resistivity (~ 1 ohm.m), and high apparent SW.
- Asia > Middle East > UAE > Arab Formation (0.99)
- Asia > Middle East > Qatar > Arabian Gulf > Rub' al Khali Basin > Bul Hanine Field (0.99)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Carbonate reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- (3 more...)
3D Modeling of the Arab Formation (Maydan Mahzam Field, Offshore Qatar): An Integrated Approach
Al Emadi, Ahmed Abubakr M. (Qatar Petroleum) | Jorry, Stephan (Beicip-Franlab) | Chautru, Jean-Marc (Beicip-Franlab) | Caline, Bruno (Total E&P France) | Blum, Marie-Stephanie (Beicip-Franlab) | Jedaan, Nizar Mohamad R. (Qatar Petroleum) | Fryer, Vance I. (Qatar Petroleum) | Leandri, Patrick (Beicip-Franlab) | Fraisse, Christian (Total)
Abstract The Late Jurassic Arab Formation consists of complex carbonate and evaporite facies associations deposited along ramps and intra-shelf Arabian basins, which form large hydrocarbon fields. Most of the time, the 3D reservoir characterization of such reservoirs is challenging, due to superimposed diagenetic overprints. The aim of this paper is to present an integrated approach using original rock-typing and modeling methods for the characterization of the four main reservoirs of the Arab Formation in Maydan Mahzam Field (Qatar). A sedimentological study was conducted on cores, and a sequence stratigraphy framework was developed. Three depositional models are proposed to illustrate the progradation of the Arab D carbonate platform toward the Southeast and the deposition of inner ramp/sabkha facies of the Arab A, Arab B and Arab C reservoirs. Rock-types that are characterized by specific geological, petrophysical and Kr/Pc properties have been defined from cores and thin sections, taking into account log response and SCAL measurements. These rock-types have been extended to all the wells by mean of a semi-interactive statistical classification applied on log data. They have been propagated in a 3D grid using a non-stationary geostatistical approach guided by 3D probability cubes. The probability cubes calculation is based on local vertical proportion curves determined from well sets and from the sedimentological models which cover undrilled areas. This paper contributes to a better understanding of the sedimentology of the Arab Formation in Qatar and helps to refine the regional distribution of the Arab D reservoir facies. It demonstrates that an accurate rock-typing scheme combined with the definition of a sequence stratigraphy framework are of prime importance for building 3D static models, which honor geological concepts for carbonate reservoir simulation.
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (1.00)
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Sedimentary Geology > Depositional Environment > Transitional Environment > Tidal Flat Environment > Sabkha Environment (0.35)
- Asia > Middle East > UAE > Arab Formation (0.99)
- Asia > Middle East > Saudi Arabia > Arabian Gulf > Arabian Basin > Arabian Gulf Basin > Berri Field > Hanifa Formation (0.99)
- Asia > Middle East > Saudi Arabia > Arabian Gulf > Arabian Basin > Arabian Gulf Basin > Berri Field > Hadriya Formation (0.99)
- (4 more...)
- Reservoir Description and Dynamics > Reservoir Characterization > Sedimentology (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Geologic modeling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Core analysis (1.00)
A Mid-Jurassic Carbonate Reservoir Case Study, Offshore Qatar: How to Capture High Permeable Streaks in a 3D Reservoir Model
Sudarsana, Agus (Qatar Petroleum) | Abdelouahab, Mariem (Qatar Petroleum) | Chanpong, Robert | Fryer, Vance I. (Qatar Petroleum) | Hall, Jonathan (Qatar Petroleum) | Vizcarra, Edwin (Qatar Petroleum)
Abstract Since few publications exist regarding the Middle Jurassic Uwainat carbonate sedimentology in Qatar, this paper contributes significantly to the understanding of Uwainat sedimentology and depositional process in Qatar and in the southern area of the Arabian Gulf. This paper also demonstrates how a detailed sequence stratigraphic framework for Uwainat, established for the first time in Maydan Mahzam and Bul Hanine Fields, was integrated with sedimentology, to build proper stratigraphic and facies models. In addition, the results of this study confirmed that a facies based model is an excellent solution for capturing and predicting the high permeable facies/dynamic rock types in their proper time/depth location within a high resolution stratigraphic cycle. Compared to previous work on Uwainat in Maydan Mahzam field, this study allowed a good and promising early history matching of the field performance. Integrating various disciplines to analyze data and build a 3D geological model of a heterogeneous carbonate reservoir is key to a proper workflow. The work flow developed for this study could be used to describe other carbonate reservoirs in the region. Introduction The Mid-Jurassic reservoirs are part of Qatar Petroleum's Maydan Mahzam and Bul Hanine offshore oil fields. These reservoirs, Araej Upper, Uwainat, Araej Lower and Izhara have been on production for 20 years. Bul Hanine (BH) and Maydan Mahzam (MM) are mature fields located Offshore Qatar some 120 kms east of Doha. In both the United Arab Emirates (UAE) and Qatar, the Middle Jurassic comprises the Izhara and Araej Formations. The Middle Jurassic is known as Dhruma Formation in Saudi Arabia and other places in the Arabian Gulf. The Araej Formation is divided into three members: Araej Upper, Uwainat and Araej Lower. The Uwainat reservoir is the middle member of the Araej Formation (Bathonian-Callovian age) and is considered as the most significant horizon of the Middle Jurassic Formations. The Uwainat thickness, approximately 180 feet, is relatively uniform throughout the southern area of the Arabian Gulf and consists of 5 to 20 ft thick sedimentary cycles of alternating low permeability lime wacke-/packstones, and 0.5 to 5ft thin relatively permeable pack/grainstone layers. The grainstone layers, which impact reservoir performance, cannot be reliably detected directly from logs. Diagenesis plays a crucial role in reservoir development. The main diagenetic processes are early compaction, early leaching, dolomitization, cementation, stylolitisation and late leaching. In the main porous wack/packstones porosity is mainly of the leached secondary fine inter-particle and leached secondary intra-particle type. In the permeable grainstone beds, primary and secondary inter-particle/granular porosity are the dominant pore types. The dominant grain types in the Uwainat sediments are pellets/peloids, benthonic foraminifera, echinoderm, shell fragments and mud. Corals are especially common in the upper part of the Uwainat reservoir and oncoids appear only in the lower part. Most of the grains are largely micritized. Throughout the Uwainat, sediments have been affected by bioturbation. The Uwainat sediments were deposited in a shallow marine shelf environment, the nature of which is slightly restricted in the lower Uwainat, and normal marine in the upper Uwainat. The overall energy of deposition is moderate to high. The grainstone layers within the Uwainat, which impact reservoir performance, cannot be reliably detected directly from logs because of their limited thickness. The better porosities and permeabilities occur mainly in the upper half of the reservoir.
- Asia > Middle East > Qatar > Arabian Gulf (0.88)
- Asia > Middle East > Qatar > Ad-Dawhah > Doha (0.24)
- Geology > Sedimentary Geology (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Dolomite (0.48)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying (0.93)
- Asia > Middle East > Qatar > Arabian Basin > Arabian Gulf Basin > Dukhan Field (0.99)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Upper Marrat Formation (0.98)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Sargelu Formation (0.98)
- (3 more...)
Monitoring of Real-Time Temperature Profiles Across Multizone Reservoirs during Production and Shut in Periods Using Permanent Fiber-Optic Distributed Temperature Systems
Fryer, Vance I. (ConocoPhillips) | Dong, Shuxing (ConocoPhillips) | Otsubo, Yujiro (Schlumberger) | Brown, George Albert (Schlumberger Sensa) | Guilfoyle, Paul (Schlumberger)
Abstract This paper describes the use of a fiber-optic distributed temperature system (DTS) to monitor and evaluate the production and shut-in thermal profiles in an offshore China well. The objective was to identify and correlate production changes with respect to time over the first phase of a multi-phase offshore field development. The well was drilled from an offshore platform with a deviation of 40 degree across the reservoir section and completed with a 5 ๏ผฟ inch diameter expandable sand screen (ESS). An electrical submersible pump (ESP) was used to produce the oil. The reservoir consists of multi-layered sand zones and the flow was commingled through the sand screens to the pump intake set in a 9โ5/8 inch diameter casing. The system was commissioned to acquire a better understanding of the flow allocation in the complex stacked reservoir sequence. The importance of this knowledge in the early stages of production is expected to influence future field development. Continuous distributed temperature monitoring of the well enabled quantitative analysis of the produced fluids to be performed at selected times providing real time, permanent, production monitoring over the reservoir. This technique will allow future wells to be developed with smaller completion sizes by limiting the requirement for production logging "Y" tools. The data acquired to date has provided improved reservoir characterization and understanding of the dynamics of the reservoir behavior. The data analyzed included initial well unloading and clean-up, zone depletion over time resulting from zone reservoir pressure changes, natural flow on shut-in and differential flow induced from various production rates using a variable speed ESP. These key events would not have been captured with conventional production logging due to normal operating constraints. As the completions in this field are multi-zone or multi-layer completions, understanding the relative flow contribution of each zone or layer is important for long-term reservoir management.Combined with pressure transient analysis of initial production history, the data collected from the fiber optic DTS has enabled the determination of individual sand lobe flow capacity and a better determination of net pay cut offs.Combined with other open-hole log information, a breakthrough has been achieved for generating accurate models of permeability for each sand sequence within this fluvial deltaic reservoir environment. Fiber Optic System Installation and Operation The distributed temperature system optical fiber was installed in a ๏ผฟ inch diameter 316 control line attached to the 3๏ผฟ inch diameter production tubing and supported across the reservoir interval by a 2 3/8 inch EUE stinger hung below the REDA* electrical submersible pump (ESP) and packer assemblies. The production tubing is hung by 4 1/5 inch diameter tubing from a Drill Quip tubing hanger. The fiber was installed in "single ended" format (only one fiber) using encapsulated control line along the reservoir interval for protection and bare control line elsewhere. A twin check-valve and a burst disc assembly were used at the bottom of the control line to provide a dual barrier to the formation. The control line was installed using mid-joint and cross coupling protectors along the stinger (deviated section). The stinger and encapsulated control line are run inside an expandable sand screen (ESS) across the reservoir section, which is 374 meters in length. The well completion diagram is shown in Fig.1.
- Asia (0.88)
- North America > United States > Texas (0.47)
- Europe > United Kingdom > England > Hampshire Basin > PL 089 > Block 98/6 > Wytch Farm Field > Sherwood Formation (0.99)
- Europe > United Kingdom > England > Hampshire Basin > PL 089 > Block 98/11 > Wytch Farm Field > Sherwood Formation (0.99)
- Europe > United Kingdom > England > Hampshire Basin > PL 089 > Block 97/15 > Wytch Farm Field > Sherwood Formation (0.99)
- (5 more...)
- Well Completion > Sand Control > Screen selection (1.00)
- Well Completion > Completion Monitoring Systems/Intelligent Wells > Downhole sensors & control equipment (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
ABSTRACT A 5-year program to reactivate 103 inactive wellbores in four mature oil and gas fields in southern Louisiana commenced in October, 1990. The program consists of an engineering and geologic evaluation of the reservoirs penetrated by each wellbore. Pulsed-neutron-capture (PNC) log data has proven to be the most effective and widely used diagnostic tool in the evaluation of remaining behind pipe reserves in the older wellbores. During the field implementation of recompletions identified using PNC data, 4 wells were found to have casing leaks which were detected by pressure testing the casing. A post recompletion evaluation of the PNC log data on these 4 wells revealed that a sharp increase in the background counts occurred at the location of every casing leak and that the character of the increase was unique in the area of the leaks. The gamma ray log used for depth correlation also showed "hot spots" in the area of the leaks as would be expected due to the deposition of radioactive salts from formation water. The depth correlation gamma ray log data showed several other hot spots throughout the wellbores that were not accompanied by the same increase in the background counts as observed iii the location of the leaks. Each well was logged under static conditions (i. e. the well was not flowing). This could provide valuable assistance in locating casing leaks during ongoing operations or identifying possible casing leaks prior to commencing major workover or recompletion operations. A similar background curve response has been noted on an upcoming workover candidate in one of the fields. The procedure for this well has been modified in anticipation of the suspected leak. The unique response noted in these field examples is currently being investigated. Some possible explanations currently under evaluation are:The radioactive salts deposited on the casing in the damaged area are activated by the neutron source, resulting in a higher measured background radiation level, Assumed static well conditions were incorrect, and water flow occurred through the leak which in turn was activated by the neutron source and detected by the background gamma ray detectors, The increase in the background counts is due to the deposition of radioactive salts only and not affected by the neutron source, in which case an insensitive scale on a standard gamma ray log would yield the same results. This latter explanation appears least likely as other hot spots have been noted without the corresponding increase in background counts.
- North America > United States > Louisiana (0.34)
- North America > United States > Oklahoma (0.28)