bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Pore Network Characteristics on Steady-State Two-Phase Flow Based on a True-to-Mechanism Model (DeProF)
Authors: Valavanides Marios S. , Payatakes Alkiviades C.
Published: December 2007

In the recently developed "DeProF" model steady-state two-phase flow in porous media (SS2φPM) is modelled as a composition of three flow patterns, namely CPF (connected-oil pathway flow), GD (ganglion dynamics), and DTF (drop traffic flow). The key difference between these prototype flow patterns is the degree of disconnection of the non-wetting phase (‘oil’). The observed flow is usually a mixture of the basic prototype flows. Each flow pattern prevails over mesoscopic-scale regions of the porous medium (ranging from a few to several hundred pores), whereas the macroscopic flow is homogeneous.

The predictive capability of the DeProF model was used to investigate the effect of pore network geometry and topology on the pore scale mechanisms of two-phase flow in pore networks. The domain of the values of the operational parameters Ca and r, for which two-phase flow is sustained, is determined by performing simulations of two-phase flows in 2-D and 3-D pore networks and for various combinations of fluids. Macroscopic interstitial physical quantities that characterize two-phase flow are computed.
Data Management and Quality Control in the Petrophysical Environment
Authors: Al-Farisi Omar , Dajani Nasser , Boyd Douglas , Al-Felasi Ali
Published: December 2007

Petrophysics gathers, evaluates, distributes and stores well logs, processed and interpreted data. These data are important, as it affects the outcome of reservoir decisions determining oil company profitability. Recognizing this, oil companies invest considerable amount of money and time in its acquisition. For a reasonably active drilling program, the data flow is continuous and unrelenting. Unless the data acquisition process is well controlled, quality can suffer. To efficiently manage and ensure high quality data streams, we developed a data process control system called UPIC (Universal Petrophysics Integrated Control). The system monitors and controls well log data flow through documentation. It addresses operation programming, data acquisition, job follow-up, quality, safety, interpretation, data archiving, training, cost control, petrophysical studies, developments and points out where improvements can be made. This paper presents our first two years' UPIC experience.
Jay Nitrogen Tertiary Recovery Study: Managing a Mature Field
Authors: Lawrence J. J. , Maer N. K. , Stern D. , Corwin L. W. , Idol W. K.
Published: December 2007

The Jay field produces a light, sour crude from the Smackover carbonate at a depth of 15,000 feet [4600 meters]. Jay has been undergoing a miscible flood using alternating nitrogen and water injection since 1981. A third-party air liquefaction plant supplies the nitrogen; current injection rates are 77×106 scf/D [2.2×106 m3/D] of nitrogen and 170,000 bbl/D [27 000 m3/D] of water. The overall oil recovery at Jay is expected to approach 60% of OOIP with recoveries approaching 70% in the Upper Smackover formation. Incremental recovery from miscible nitrogen injection is estimated to be 7-10% of OOIP.

Most wells in the Jay field were cored, providing detailed rock properties for construction of valid and useful geologic and reservoir simulation models for reservoir management. Extensive core descriptions have identified cemented zones associated with stylolites as baffles to vertical flow. Recognizing, the resulting low vertical permeability, coupled with high horizontal permeability in the dolomite facies, has been the key to the high oil recovery.

Reservoir simulation has been an integral part of the development and operation of the Jay field. The latest full-field flow simulation model is derived from a new geologic model that incorporates sequence stratigraphy, the latest geostatistical methods, and a stylolite model. The flow simulation model is also more finely gridded than previous models and includes an updated fluid characterization treatment making possible simulation of processes that could not be accurately modeled previously. The history match of this model entailed well by well matches of production and pressure data for all 137 wells in the field.

Full-field flow simulation models of Jay have historically been used to evaluate the benefits of extending nitrogen injection, recycling produced nitrogen, and increasing water injection rate. Recent studies using the updated full-field model have been performed to optimize nitrogen distribution among patterns, investigate low-pressure operation, evaluate dedicated Lower Smackover wells, assess full-wellstream injection, and evaluate conversion of producers to injectors. Based in large part on these simulation studies, several major initiatives have been undertaken that extended field life by more than ten years.
Waterflood in Vuggy Layer of a Middle East Reservoir - Displacement Physics Understood
Authors: Dabbouk Chawki , Ali Liaqat , Williams Glyn , Beattie Garry
Published: December 2007

Early water breakthrough has occurred in this giant Middle East reservoir. This has posed fresh challenges for maintaining plateau production and achieving a high recovery factor. Possible reasons for this early breakthrough are flow through vuggy, thin high permeability, and fractured layers. The stylolitic layers are also probably inhibiting water slumping, which maintains water in the "thief" layers. Poorly understood aspects are the amount of these rock types contributing to the rapid water transport, effective permeability and the amount of oil from these layers that is recovered by waterflood. This paper describes the results of an innovative study that reduces the uncertainty in water breakthrough prediction, and recovery efficiency, from a vuggy lithotypes layer.

The results of this study show that: The ultimate waterflood recovery efficiency from vuggy (rudist) rock was high and the oil was not by-passed in the vugs. Ultimate residual oil saturation was ∼24%.A simulated horizontal waterflood displacement from a vuggy rock predicted ∼30% less dry oil production at breakthrough compared to that of an equivalent homogeneous lithotype waterflood.

New technology developments were required to complete this study. These developments included waterflood of a whole core at full reservoir conditions using X-ray CT (computed tomography), a technique for conducting sophisticated flow studies on fragile, under gauge core at full reservoir overburden, and a technique for achieving initial water saturation in highly heterogeneous core. The study also provides new insights into the complex spatial arrangements of lithotypes, and a detailed 3 dimensional coreflood simulation match in a complex heterogeneous system.
Waterflood Saturation Measurement with Carbon-Oxygen Tools In a Middle-East Carbonate
Authors: Chandran T. P. R. , Vervest Edwin , Brown Matt , Al Hajeri Mubarak , Al-Anzi Ealian , Najeh Hamad , Chakravarthi Ravula
Published: December 2007

This paper details a program to test saturation logging in a Middle East carbonate reservoir that recently began a secondary recovery project. The ability to measure oil and water saturations in the target flood zones is critical for optimizing recovery and finding unswept zones. Water saturation is typically determined using a pulsed neutron capture logging tool (PNC). The PNC differentiates between the neutron capture cross-section of high salinity water and hydrocarbon. In the case of this waterflood, seawater is injected, with a salinity of 25,000 ppm. This seawater has a similar neutron capture cross-section to the oil in the formation, making PNC tools unsuitable for determining water saturation in break through zones.

A test program was developed to determine the reservoir fluid saturation using carbon-oxygen (C/O) logging techniques. The new generation through-tubing C/O tools with higher measurement resolution enables detection of low salinity seawater. The test program consisted of a log-off between three logging service companies providing C/O tools. The C/O derived saturations were compared to the open hole log saturations and to PNC saturations in two wells in the waterflood pilot area – a comparison that was possible since the injected fluid in the pilot was high salinity formation water.

Most of the wells in the waterflood area are completed with dual tubing strings. The saturation logging target interval is generally in the short string of the dual completion, making wireline surveillance difficult. The test program also evaluated the ability of the contractors to log in a dual environment. This paper details the results of the C/O test logging program and provides recommendations on future saturation logging requirements for this type of reservoir.
Sequence Stratigraphy and Sedimentation of the Araej Formation (Middle Jurassic), UAE: Outcrop and Subsurface Compared
Authors: de Matos José Esteves
Published: December 2007

A comparison of the Araej section cropping out in Wadi Naqab (southeast of Ras Al Khaimah in the UAE) with the subsurface of Abu Dhabi and nearby areas shows that the Araej Formation of onshore and offshore Abu Dhabi is very similar to that of Qatar. The surface section was compared to well data using core petrography, biostratigraphy, characterization of the cycles and depositional environments and sequence stratigraphic analysis.

The Araej Formation corresponds to the section between the top of the Izhara and the base of Tuwaiq Mountain Formation. The age of the Araej section of Wadi Naqab succession, similarly to the subsurface, ranges from Bathonian to Callovian.

In Wadi Naqab, the cyclic section equivalent to the Araej Formation comprises five sequences. The recently defined Arabian Maximum Flooding Surfaces, J30 and J40 are evident in Wadi Naqab. J30 coincides with the MFS of the first Bathonian sequence, in the lower part of the Lower Araej, while J40 can either be located near the top of Uweinat or near the base of Upper Araej.

The Uweinat is composed mainly of grainstones, micropeloidal in the lower and middle parts and oolitic and cross-bedded in several horizons throughout the section. Stromatoporoid and coral rudstones occur in the upper half. The Uweinat of Wadi Naqab seems similar to the offshore Uweinat reference section of well US-2, where reworked stromatoporoides were also recorded in the upper Uweinat.

As a result of regional correlations, the Araej section of a well of NE Abu Dhabi is proposed as the onshore reference section of the Araej Formation of Abu Dhabi.

The Sequence Stratigraphic interpretation with the identification of the Maximum Flooding Surfaces provides better chronostratigraphic control enhancing prediction accuracy of the geometric relationship of source, reservoir and seals. A better characterization of the Araej Reservoirs will support the regional correlation, exploration and production of the Middle Jurassic of the Middle East.
The Challenge of Improving Water Quality Prior to Discharge to the Sea During Well Clean Up and Testing Operations by the Rig/Barge
Authors: Sharkh AF. Abu , Fadaq A. S. , Kikuchi S. , Al Attas M. O. , El Housani Housam , Morrison Evan , Malash Karim
Published: December 2007

Currently, all ZADCO/ADMA-OPCO wells are acid stimulated to remove formation damage and improve WELL PRODUCTIVITY. The low PH of the returned fluid during the back-flow of the acidized wells have an adverse impact on the production lines, down stream facilities, and environment.

Currently, ZADCO/ADMA-OPCO have been implemented successfully the Oil Re-Injection system with acid neutralization Process and achieved Zero oil flaring, zero gas flaring in high potential wells and improved the quality of water dumped to the sea down to 100 ppm oil in water, yet, it does not meet HSE requirements of 15 ppm.

Therefore, we have studied jointly with service providers various technology in order to achieve the HSE requirements. Selected the following two systems for trials:

➢ The 1st system (de-oiling) is mainly consisting of a degasser, hydro cyclone, reject oil tank, pumping units and control panel all on one skid. ➢ The 2nd system is a two-stage treatment process using patented adsorption media.

In this paper we will discuss the process description, field trial data, impact on the environment and other related technical information.
Utilization of a PhaseTester, MultiPhase Flow Meter in Cleanup and Testing Operations
Authors: Al Attas I. , Al Suwaidi I. , Sharekh A/F Abu , El-Khazindar Y.
Published: December 2007

The combustion efficiency of fully atmospheric oxidation is insufficient. Oil- and gas-flaring operations create significant amounts of emissions that contain unburned hydrocarbons, carbon monoxide and nitrogen oxides, which produce acid rain, smog, ozone at ground levels, and greenhouse gases in the upper atmosphere.

Acid rain depletes soil, pollutes water, damages forests, endangers animal habitats and food chains, and corrodes human-made structures, such as buildings, statues, automobiles, and other artifacts made of stone or metal. Smog and ozone cause human respiratory ailments, such as asthma, bronchitis and emphysema. Most scientists believe that greenhouse gases are a major cause of global warming. Increased concentrations of water vapor, carbon dioxide, methane and other greenhouse gases trap heat energy in the earth's atmosphere. A gradual rise in the earth's surface temperature is expected to melt polar ice caps and glaciers, expanding ocean volume and raising sea level, flooding some coastal regions and even entire islands.

Middle Eastern countries, including the U.A.E. with its low-lying coastal areas, are concerned about rising sea levels and potential flooding caused by global warming. They are concerned about increased radiation of heat and light from global warming, leading to regional desertification. As major producers of oil and gas, they are concerned about the deterioration of air quality from inefficient combustion of a sour gas supply.

Abu Dhabi is blessed with a charming environmental heritage. Nevertheless, the environment in this part of the world is no less fragile than anywhere else.

Recognizing mounting concerns over environmental issues, a joint task force was formed in June 1997. The Abu Dhabi Marine Operating Company and the Zakum Development Company, with the assistance of Schlumberger, the contracted service provider, worked together as one team to implement new solutions for optimizing acid neutralization, reducing flaring operations in the short term, and ultimately achieving zero hydrocarbon flaring to eliminate environmental risk during well-testing operations(1–3).

In an effort towards realizing ADNOC's HSE guidelines towards eliminating Oil and Gas flaring during testing and cleanup operations, a Phase Tester, Multiphase flowmeter was utilized offshore Abu Dhabi during clean-up and testing operations, leading to a reliable flow rate data, safer and more environmentally friendly operations. The deployment of the Phase Tester, Multiphase flowmeter lead to eliminating the gas flared by 100% during the post cleanup operations and thus decreasing the total amount of gas flared during cleanup and testing operations by 60-70%.
Recent Developments in High-Temperature Acidizing with Super 13Cr Completions: Laboratory Testing
Authors: Nasr-El-Din H. A. , Al-Khuraidah A. S. , Kritzler T. , Cassidy J.
Published: December 2007

Saudi Arabia embarked on an aggressive development of new gas fields to meet the increasing demand for natural gas and gas condensate. Therefore, it became necessary to further develop gas reservoirs. However, the reservoirs presented challenging conditions such as temperatures up to 275ºF, H2S contents up to 10 mol% and CO2 contents higher than 2 mol%. Previous completions utilized regular low-carbon steel (L-80 and C-95) metallurgy. Due to the nature of the reservoir conditions, these types of completion hardware could not be applied in areas where H2S content is very low and CO2 is high. Super 13Cr completions have been proven to be reliable in these environments. However, Super 13Cr completions cannot tolerate the high acid concentrations (28 wt% HCl Acid) that are needed to acid fracture the tight carbonate formations available in Saudi Arabia. Therefore, a special acid blend and corrosion inhibitor package had to be developed to effectively stimulate the carbonate formation through these types of completions.

This paper will present how the aforementioned problem was overcome by developing an acid blend using 15 wt% HCl and 9 wt% formic acid. Initial laboratory tests showed high corrosion rates for the Super 13Cr coupons when this acid formulation was applied. However, due to an intensive research effort, an effective corrosion inhibitor package was developed for Super 13Cr completions using this acid system. Several corrosion inhibitors and inhibitor aids were tested. Compatibility of various additives was conducted and corrosion tests were performed at bottom-hole conditions. As a conclusion, a new corrosion package was developed for Super 13Cr tubing. This package is compatible with reservoir fluids and other acid additives. In addition, it produces acceptable corrosion rates with no pitting.
A Poroelastic Analysis to Address the Impact of Depletion Rate on Wellbore Stability in Openhole Horizontal Completions
Authors: Salamy Salam P. , Finkbeiner Thomas
Published: December 2007

This paper highlights the development of a coupled poroelastic geomechanical and fluid flow model which incorporates field and lab data with the objective to constrain the full in-situ stress tensor and rock strength in order to predict the stability of open hole horizontal completions during reservoir depletion.

Results of a four-year comprehensive testing and monitoring program conducted to assess the extent of hole instability during shut-in and flowing periods1 indicated that there was no immediate hole collapse. However, the study revealed the need to assess the long-term impact of reservoir depletion and pressure drawdown on wellbore stability.

The results of this study indicate that the in situ stress state can be characterized by a normal faulting environment with low differential stresses in which the maximum principal stress is approximately equal to the overburden. Furthermore, a detailed analysis of wellbore stability during production supports openhole completion for horizontal wells under the condition that reservoir depletion is limited to a maximum pressure drop of 1,500 psi. This finding is independent of well azimuth. Pressure drops exceeding 1,500 psi in the reservoir are likely to cause considerable wellbore instabilities. These results were achieved under the assumption of moderate to more pronounced amounts of drawdown (500-1000 psi) in the near wellbore region. The study also highlighted that laboratory-derived rock strength values from triaxial tests, are low and are not consistent with the drilling and production experiences to date in the field. Rather, the formation appears to behave in a plastic manner that strengthens the wellbore.
Gas Sweetening Process - Problems and Remedial Measures
Authors: Osman Khaled W , Vasagam Manicka
Published: December 2007

Gas sweetening plant of an LNG train is a vital operating unit, where the sour contents (H2S and CO2) of the feed gas are removed to make it sweet for processing downwards to produce LNG. Any improper removal of sour gases from the feed natural gas would directly affect the quality of LNG and pose operational problem in Cryogenic column, where the LNG is produced. Besides the above, any problem in the Gas sweetening plant would reduce the gas handling capacity and in turn reduce the LNG production rate, which means loss of revenue. A severe operational problem was encountered during early 2001, in ADGAS' LNG Train-3 Gas sweetening plant. Through this article ADGAS shares their operating experience and describes the evaluation of the problem, successful remedial measures adopted and benefits derived.

Abu Dhabi Gas Liquefaction Company (ADGAS), as a part of ADNOC (Abu Dhabi National Oil Company) group, was formed in the year 1973 and started production in 1977 from their industrial facilities located on Das Island. Presently ADGAS operates at a capacity of around 8 million tons per year of LNG, LPG, C5+ and Liquid Sulphur as co-products. ADGAS was a pioneer in setting up the first combined LNG and LPG production facility in the Middle East.

ADGAS operates three LNG Trains. The first two Trains (Train 1 & 2) have been in operation since 1977, each operating at a capacity of 180 tons per hour of LNG. The third one (Train-3) was commissioned in 1994 with a capacity of 380 tons per hour of LNG.
Optimize Drilling Costs and Improving Safety, Environment and Operational Performance by Utilizing a Barge, an Abu Dhabi Experience
Authors: Darwish M. Ramzi , Nabucet M. , Cabillic J. , Metwalli Y. , El-Khazindar Y.
Published: December 2007

To comply with ADNOC HSE guidelines, ADMA-OPCO HSE Management System, and to align with ADMA – OPCO management objectives to optimize drilling costs, ADMA-OPCO and Schlumberger, the contracted service provider worked in an integrated team to realize these objectives, focusing on improving HSE efficiency, and effectiveness by utilizing innovative techniques and proactive processes on board of a multi-purpose service vessel (MPSV).

Integrating a qualified and familiarized team, working with a fit for purpose set-up to develop and ensure that a unique quality control system is in place to safely carryout the post rig operation well evaluation phase with economic practices. As a result, the operational risks are reduced, and quality wells were obtained within a high level of health, safety, and environmental assurance. This assurance has been achieved through specified minimum safety training requirements, risk assessment studies, permanent equipment installation, and pre job evaluation. The end result has been of great benefit to all parties due to eliminating the risk associated with loading/off-loading, or switching from one set up to another. Consequently more than 56 wells have been successfully serviced from February 2001 to February, 2002 (one complete year of operations) with No LTI and No LTA.

Through an equipment redundancy system, and innovative technology, environmentally friendly operations were achieved. The use of an oil re-injection system, and the multiphase flow meter eliminated oil flaring completely, as well as the gas during the flow test periods. The gas flaring was reduced by more than 60% during the whole operation.

Due to the improved HSE performance described, an additional achievement and benefit was represented by a substantial cost reduction compared to the conventional practices. The new practices adopted have lead to better utilization of ADMA-OPCO rig fleet.

These proven practices will be implemented in other fields, where ADMA –OPCO is operating, and will be extended to other ADNOC group offshore companies.

The introduction of Multi-Purpose Service Vessel with a permanent set up and one specialized, well trained crew to carry out well evaluation phase, instead of the rig conventional way had a direct positive impact on HSE performance and reduced the drilling operation costs.
Commissioning and Start-Up of a "Grass Root" Gas Project
Authors: Saadawi Hisham
Published: December 2007

Commissioning and start-up of large gas projects is a project in its own right, running in parallel to the main project. It requires years of advance planning. The management and detailed planning of this phase is crucial to the smooth transition from construction to operation.

This paper discusses the commissioning and start-up aspects of large projects in the oil and gas industry. These aspects are addressed in the context of a major "grass root" project which has been recently commissioned in Abu Dhabi.
Microbial Monitoring to Minimise Corrosion and Formation Damage in the Oil Industry
Authors: Spark I. , Mutch K.
Published: December 2007

It is accepted that sulphate reducing bacteria (SRB) and certain general heterotrophic bacteria (GHB) can promote pit corrosion of topside and downhole equipment and cause formation damage in the reservoir including H2S souring. In order to inhibit microbial growth and hence minimise these damage mechanisms, it is necessary to impose a strict microbial monitoring regime that can be used to optimise any biocide treatments. There are two major considerations relating to microbial monitoring which must be taken into account which are planktonic microbes (those in suspension) and sessile microbes (those attached as a biofilm). By monitoring the numbers of SRB/GHB entering and leaving each component of the topside process system it is possible to determine whether each is under good microbial control. If numbers are found to increase from inlet to outlet, then biocide treatment at a suitable concentration, can be used to treat the fouled components before pit corrosion or H2S production becomes a serious problem within the component. If the biocide treatment is not performed in time the system downstream may also become contaminated. By carefully monitoring each process system including injection water, firewater, cooling medium, and production systems, it is possible to extend the process equipment lifetime considerably, resulting in a major saving in equipment replacement and lost shut down time. This paper describes the microbial monitoring techniques required to minimise corrosion, biopolymer, insoluble metal sulphide and H2S production both topside and downhole.
Reservoir Management & Simulation of Al Rayyan-An Offshore Carbonate Oil Field Under Strong Aquifer Drive
Authors: Nutakki R. , Heaviside J. , Noman R. , Al-Othman I. J.
Published: December 2007

The Al Rayyan oilfield, offshore Qatar presents an interesting case of natural water drive. This paper presents the results of investigations to understand the production mechanisms in the main producing zone in the field (Arab C). This zone is a thin, low relief Arab carbonate reservoir with high porosity and permeability. The reservoir has a strong natural aquifer drive and the reservoir pressure has remained close to the original pressure during the 5-year initial production phase. The field was developed with horizontal wells to provide sufficient productivity in the thin reservoir. The main phase of field development, planned following these studies, is now underway with the drilling of additional sidetracks and further longer, carefully placed horizontal wells. Results of the first two new wells are described.

The initial production stage experienced early water breakthrough, water cut rising at first and then stabilizing. Oil production has continued at decreasing cuts throughout the five years. The reservoir studies described in this paper were used to determine the optimum well type and placement for the main phase of development. The offtake strategy was also investigated and decisions regarding offtake rate, level of water handling and other development parameters were made under the guidance of the model results.

The modeling has provided a thorough understanding of the water and oil production mechanisms in the reservoir. When wells are put on production there is rapid coning of water into the wells. The movement of the water is primarily vertical due to the small thickness of the reservoir and the strong aquifer underneath the Arab C reservoir. The size and shape of the cone stabilizes quickly after it is formed and this leads to the characteristic leveling of the WOR curve seen in the Al Rayyan wells with time. Most of the oil produced does not come from the cone underneath the well but is produced by lateral movement of oil from the region around the well.

Results show that despite the coning of water under the horizontal wells oil recovery from the field is increased at higher offtake rates. In practice the offtake rate is limited by the capacity of the separation facilities. Well numbers and individual well rates should be designed to ensure full utilization of this capacity. This unusual result is due to the geometry of the field, which is so extreme that no economic rates produce gravity stable flow. Oil recovery becomes a function of the extent or maturity of the (natural) water-flood.
Water Saturation Computation From Laboratory, 3-D Regression
Authors: Hamada G. M. , Al-Awad M. N. J. , Alsughayer A. A.
Published: December 2007

An accurate determination of initial oil in place in the early life of reservoirs or an evaluation of a developed reservoir is required to well estimate the hydrocarbon volumes. Modified Archie formula (Sw = (a Rw / ϕm Rt)1/n) is the basic equation to compute water saturation in clean formation or suitable shaly water saturation model in shaly formation. The accuracy of water saturation value for given reservoir conditions depends on the accuracy of Archie parameters a, m and n. The terms of Archie relationship have been subjected to many laboratory investigations and even more speculations. There are many factors affecting porosity exponent, m, saturation exponent, n and tortousity factor, a. Therefore, it is very difficult to fix Archie parameters and neglecting reservoir characteristics; rock wettability, formation water salinity, permeability, porosity and fluids distribution. This paper presents a new technique to determine Archie parameters a, m and n. The developed technique is based on the concept of three dimensional-regression (3D) plot of water saturation, formation resistivity and porosity. This 3D technique provides simultaneous values of Archie parameters. Also, the 3D technique overcomes the uncertainty problems due to the separate use of formation resistivity factor-porosity and water saturation equations to get a, m and n parameters.

Two field examples are given to show the applicability of the 3-D technique in comparison with three other techniques: 1) common values of Archie parameters, 2) conventional technique and 3) core Archie parameter estimation (CAPE) technique. The comparison among the four techniques has shown that 3-D technique provides an accurate and physically meaningful way to get Archie parameters a, m and n for given core samples. Water saturation profiles, using Archie parameters obtained from the four techniques, have been obtained for the studied section in the wells. These profiles have shown a significant difference in water saturation values. This difference could be mainly attributed to the uncertainty level for Archie parameters from each technique. The effect of saturation exponent on the accuracy of water saturation computation was tested using Archie's parameters derived from conventional technique and 3-D technique in the two wells.
Identification, Quantification and Analysis of Subsurface Uncertainties Associated with Reservoir Description. Assessment of its impact on the Development of a Miscible WAG Injection Project with Horizontal Wells
Authors: Ayoub M. , Negahban S. , Gomes J. S. , Dawood A. , Mahdi A. , Al-Baker S.
Published: December 2007

This paper addresses identification, quantification and analysis of subsurface uncertainties associated with development of a reservoir description and its impact on development of a field under miscible WAG process. Uncertainty analysis is an essential part of development, engineering and production of any oil or gas reservoir. As a result of a limited number of wells in the field, uncertainties in reservoir description are great. A static reservoir model is constructed using information from 18 wells and 3D seismic. An integrated modeling approach involving geology, petrophysics and geostatistics are applied in determining final property models. Several stochastic modeling techniques are applied to build the porosity, permeability and saturation models and multiple realizations are used for the uncertainty quantification. Porosity and water saturation are modelled using the Collocated Co-kriging method with depth as soft data. The permeability model is built using the Cloud Transform technique. Core and probe-permeameter measured permeability data are used to assess the heterogeneity of permeability at different scales. Fracture analysis is conducted using image logs (FMI). A full field compositional model was built to evaluate the field reservoir performance under various development scenarios. The field has been in Early Production Scheme (EPS) since early1990 and is scheduled to come on stream by December of 2005.
Effective Permeability Modeling: Geostatistical Integration of Permeability Indicators, OffshoreAbu Dhabi
Authors: Bushara M. N. , El Tawel A. , Borougha H. , Dabbouk C. , Qotb M.
Published: December 2007

The paper describes a method for modeling reservoir true effective k incorporating k from core, fractures & well test. A 3D permeability model is developed based on detailed lithotype mapping within which horizontal matrix permeability is simulated. Comparison of modelled permeability with actual test permeability values suggests that there is a genuine permeability contribution from fractures in the reservoir. The resultant model is thus combined geostatistically with fracture k so that the final permeability matches well test permeability. We used strain field as an indicator of fracture locations and hence to flow from them. Strain field over the reservoir, which correlates with test permeability, is obtained from curvature analysis and calibrated to strain calculated from core fractures. High strain areas are set to be associated with highly fractured zones that are commonly marked by increased conductivity. Computer geostattistical module computes fracture permeability from a power-law relationship and conditions it to match interpreted test permeability in 3D space. The geostatistical method offers means of predicting fracture permeability distribution field-wide and better accounts for water encroachment trends. The results helped achieve better history match results more easily than would have been possible without the combined model.
Evaluation of the polymeric materials (DVB copolymers) for produced water treatment
Authors: Carvalho M. S. , Clarisse M. D. , Lucas E. F. , Barbosa C. C. R. , Barbosa L. C. F.
Published: December 2007

Copolymers beads based on methyl methacrylate (MMA) and divinylbenzene (DVB) were prepared by suspension polymerization technique. For the copolymer synthesis, the following reaction parameters were varied: diluent type, dilution degree and divinylbenzene content. The copolymer porosity and specific surface area (BET) were determined. The copolymers were used to prepare columns, which were tested as oil remover from PETROBRAS produced water. Columns containing only one kind of polymer (polyDVB) achieved a oil content reduction of 84.9%; containing two different polymers (polyDVB and poly(MMA-DVB)) reached 89.1%. The results showed that the distinct chemical composition copolymers can retain different compounds from the produced water. The columns can be re-used after a regeneration process.
Cuttings reinjection to shallow undersea formation: The Geomechanical acceptance analysis using hydraulic fracturing simulator
Authors: Shioya Y. , Yamamoto K. , Fujieda Tadaomi , Kikuchi Shuichi , El-Khatib Hassan
Published: December 2007

Operation availability, environmental safety, and storage capacity of the slurrified cuttings re-injection into a shallow, permeable formation off-shore Abu Dhabi was evaluated using a computer simulator for hydraulic fracturing.

For the study, Umm Er Radhuma formation of Z field is chosen as the disposal formation, meanwhile Rus formation is regarded as the cap rock over the formation for isolating injected fluid and solid from propagating to seabed. A Geomechanical model of the formations which includes stress regime, formation pressure, rock mass properties, and leak-off characteristic was established with available data from literatures, wire line logging, and water disposal history in the same formation.

The numerical model, which is developed by the authors, provides the estimation of injection pressure, fracture geometry and size, and storage volume of the slurry with a modeled injection schedules. The effect of solid particle concentration which may reduce pressure near fracture tip and cause screen off is taken into account for the fluid flow analysis and the determinatin of the fractrue geometry.
Enhancement of Stimulation Treatment of Water Injection Wells Using a New Polymer-Free Diversion System
Authors: Safwat Mohamed , Nasr-El-Din Hisham A. , Dossary Khalid , McClelland Ken , Samuel Mathew
Published: December 2007

Vertical seawater injectors for a carbonate reservoir in Saudi Arabia have an injection zone (open hole) of approximately 200 ft. This reservoir has drastic permeability variations. Acid stimulation without proper diversion normally results in undesirable stimulation of the high permeability streaks. Therefore, acid diversion plays a key role in improving both the post-acid, well-injectivity and injection profile.

Various diverting agents have been used to improve the acid distribution during acid injection, including wellbore gels, foams and in-situ gelled acids. The use of polymers is an excellent means of diversion.1,2 However, evaluation of polymeric systems has demonstrated formation damage due to residual polymer, which is considered unacceptable, especially for water injection wells.3 Conventional foams have also been tested with good success.

In the present study, the use of a polymer-free viscoelastic surfactant (VES) as a diverter system is investigated and compared with in-situ gelled acid and foams. The VES is a two-component system, and in the presence of salts, the surfactant molecules associate to form rod-like micelles. These micelles can entangle with each other and form a three dimensional network, responsible for the high viscosity of the system.4,5 This non-damaging "surfactant gel" can be broken completely by injecting mutual solvent or injection water. This added advantage eliminates the need to flow back the well following acid treatments.

Laboratory studies demonstrated up to 2-fold increase in viscosity and nearly 20-fold increase in foam stability compared to foams containing polymers. The properties of VES solutions are independent of the salinity and pH of the mixing water.

Bullheading the acid enables the operator to pump these treatments at high rates, which are needed in some cases. Pumping pressure, post-acid injectivity history and injection flow profile of several seawater injectors indicate good stimulation results and better acid diversion across the whole target zone.

This paper presents the first application worldwide on the use of VES technology in water injection wells. A total of six stimulation treatments were performed using this technology, one treatment using coiled tubing (CT) and five by bullheading.

The VES technology provides a solution for heterogeneous carbonate reservoirs, and eliminates formation damage induced by the polymers present in the conventional diversion systems. Stimulation using the VES system on six wells resulted in an injection increase of more that 45,000 bbl of water per day, much higher than similar treatments where conventional foams were used.
Automated well control increases performance of mature gas-lifted fields, Sendji case
Authors: Boisard O. , Makaya B. , Nzossi A. , Hamon J. C. , Lemetayer P.
Published: December 2007

This paper reviews one recent example of benefits of the implementation of a full control of wells tool offshore Guinea Gulf.

This field case confirms the full control of wells smart automation increases by 10% the daily oil production of a mature field. It also confirms production increase above 20% under sensitive situations.

Using measurements and adju stments only at well head avoids work over and ensures robustness. Setting parameters related to physics such as ranking or starting lift gas tunes the standard sequences to any well and topsides.

Other fields applications include dual gas lift and dynamic control of gas coning to maximize recovery.

Upgrading the well control to digital allows a remote operation. High quality data improves understanding the behavior of mature wells.

Beyond this supervision, two levels of control algorithm provide with a continuous and autonomous control of the unmanned platforms.

This smart control monitors and automates both single well and platform levels to handle transient phases and to face unforeseen behavior of reservoir, wells and facilities. Automated sequences help the operators if any trouble on a well or topsides. Remote manual operation cannot account continuously and accordingly for many wells particularly during hurried restart phases.

This smart control increases the uptime and efficiency of wells and topsides. It stabilizes at source the compression and topsides intake. It also increases the recovery factor.
Introducing an Enhanced Calibration Technique for Core-Log Rock Mechanical Parameters: New Shift Calibration and Recursive Filtering Techniques
Authors: Awal Mohammad R. , Mohiuddin Mohammed Ahmed
Published: December 2007

We have developed two new methods for core-log data calibration. These methods are applied in tandem (in series). We have demonstrated that the new approach in calibration may result in an order of magnitude of difference. The results can significantly alter the way various well designs are done, including hydraulic fracturing, optimized borehole trajectory, and well intervention.

Traditionally, the measurements of rock properties have been based on cores. However, the coring process has always been considered to be costly, and mitigated by dependence on logging. Although logging provides a distinct advantage by providing continuous (at least at a half-foot depth interval) measurements of data, the core-based measurements are still considered superior and more reliable. Hence log-based data are calibrated in terms of the limited core-based data.

The most common method applied is the least squares method (Ahmed, 1988). However, the least squares process alters the quality of the log-based data, not only in magnitude but also in trend. It is the second aspect of data alteration that is questionable. It may smear the true variability of rock properties change as a function of depth. We have found, with actual well data, that the smearing of data trend may occur to the extent that a flat response may result where actually the rock property varies rapidly with depth. Maintaining the true rock property change with depth, for example, the uniaxial compressive strength (UCS), can be crucial in designing a successful hydraulic fracture job. Since it is highly desirable to contain the fracture height within the payzone, the accurate UCS values in the over- and the under-burden rock strata must be known with respect to that in the payzone. Similary, accurate zonal permeability information in necessary in order to diagnose thief zones, and/or shut-off water producing zones.
Development of a Petroleum Contractual Strategy Model
Authors: Ramadan N. B. , Zekri Abdulrazag Y.
Published: December 2007

The development of a petroleum exploitation strategy is essential for any country, which needs to develop its indigenous petroleum resources, see Fig. 5. A petroleum exploitation strategy is the series of policies relating to licensing, taxation, royalty, and general legal instruments i.e. contractual agreements, see Table 1 developed by the state in order to ensure the orderly development of petroleum exploration and production. In the absence of a clear petroleum exploitation strategy, the international oil companies would not be able to assess the political and economic risks involved in any petroleum exploitation venture, no matter how low the technical risks are.

Since the International Oil Companies are major sources of the intensive capital, and sophisticated technologies needed for exploration and development of petroleum resources, it is essential for a country to formulate a coherent and well balanced petroleum exploitation strategy. This should be consistent with its social and economic goals and at the same time allow the international oil companies to generate economic profits that in some way relate to the level of risk involved in obtaining these profits. This research project has focused on the study of the different petroleum contractual agreements between host countries and international oil companies worldwide, and has culminated by the development of a contractual strategy model for the exploitation of the petroleum resources. The development of the model has been preceded by a comparative and evaluative analysis of the international and host country petroleum agreements. The main features, advantages and disadvantages of each type have been summarized and tabulated. The suitability of the different agreements, in the view of the rapidly changing environment of the petroleum industry, has been evaluated. A new contractual model for the exploitation of petroleum resources in the Middle East is developed in this project. The Model required the development of eight different strategies, which relate to the possible combinations of three strategic factors that were found to be of the greatest importance. It has been proposed to use this model to evaluate and guide the development of the future Middle East petroleum exploitation strategies.
A New Ion Exchange Process for Softening High TDS Produced Water
Authors: Brown Craig , Sheedy Michael
Published: December 2007

Weak acid cation (WAC) resins are normally utilized for softening high TDS produced water. The main disadvantage of the WAC process is that the resins require regeneration with hydrochloric acid followed by sodium hydroxide. This is expensive and necessitates the utilization of exotic, corrosion resistant alloys for construction.

Strong acid cation (SAC) ion exchange processes employing only brine regeneration (i.e. no acid or caustic) are much simpler and less expensive, however the SAC process is normally restricted to low TDS (<3000 mg/L) waters. A new ion exchange softening flow-sheet that uses brine regeneration has been developed based upon the Recoflo short-bed ion exchange process. Recoflo makes it possible to use extremely high service flow rates through very short (15 cm) resin beds, while achieving low hardness leakages. The key to applying this to high TDS produced water is the use of high purity brine regenerant. A novel ion exchange process which employs only water for regeneration (i.e. no chemicals) has been developed for purifying the brine. This paper explains the rationale for the process using ion exchange equilibrium calculations and then shows pilot plant and field data.
New Tools for Heavy Oil Dehydration
Authors: Warren Kenneth W.
Published: December 2007

Heavy oils are becoming increasingly attractive from the standpoint of availability of reserves and economic status as "opportunity" feedstocks. However, they also bring some complex dehydration problems including high levels of suspended solids, conductive organic species, and varying amounts of semisoluble and precipitated organic materials. Meeting these challenges requires new techniques in both the areas of chemical treatment and dehydrator design. This paper focuses upon improvements in hardware design.