bluuebunny/crossref_metadata_2025 huggingface dataset:
The Wafra Second Eocene Heavy Oil Carbonate Reservoir, Partitioned Zone (PZ), Saudi Arabia and Kuwait: Reservoir Characterization, Modeling, and IOR/EOR Evaluation
Authors: Meddaugh W. Scott , Frydl Paul , Dvoretsky Rachel , Gross Steve , Al-Gamdi Saleh , Dull Dennis , Johansen Steve , Caldwell Gary
Published: December 2013

The Paleocene-age Second Eocene reservoir is the second shallowest major reservoir in the giant Wafra Field. The reservoir is part of the Umm Er Radhuma Formation. It occurs at a subsea depth of 1,400 feet and consists of approximately 400 feet of porous dolomite and minor anhydrite deposited on a shallow carbonate ramp. The lower reservoir consists of shallow subtidal sediments; the upper contains stacked subtidal-dominated cycles with thin intertidal/supratidal capping beds. The average porosity is about 30% and permeability average near 300 mD.

Recent stratigraphic and diagenetic studies have improved the characterization of this important heavy oil reservoir. Pervasive dolomitization by seepage reflux of evaporated seawater altered the original depositional fabrics and pore systems. The major diagenetic trends are clearly related to the sequence stratigraphy. The upper portion of the reservoir, informally known as the 1¾ Eocene, is finely crystalline and largely preserves the original subtidal to intertidal/supratidal depositional fabric. The lower reservoir known as the 2nd Eocene, is coarser crystalline and generally lacks discernible depositional fabric. Oil production comes mainly from the lower portion of the reservoir that is characterized by higher permeability, fabric-destructive subtidal dolostone.

Prior to commencing dynamic modeling an EOR screening exercise was completed. Of the eight EOR options considered, only steamflooding and waterflooding were found to be the most viable choices and are the focus of work to date. Updated full field, geostatistical models were generated with reservoir property distributions constrained by stratigraphic layer and the available well and core data. Following up-scaling and history matching, the dynamic model will be used to re-evaluate numerous development options including continued primary development, infill drilling, waterflooding, and continuous steamflooding using various pattern sizes and configurations. Early results from this work along with results from a prior similar study suggest that steamflooding yields higher recovery than other options and that waterflooding also yields good incremental recovery.
Reactivating a Tight Carbonate Reservoir in the Greater Burgan Field: Challenges, Options and Solutions
Authors: Chimmalgi V. S. , Al-Humoud Jamal , Al-Sabea Salem , Gazi Naz , Bardalaye Jayanta , Mudavakkat Anandan , Al-Enezi H. , Al-Zankawi O. , Ahsan J. , Abdulrazzaq E. , Tirkey N. , Kotecha R. , Snasiri F. , Jalan S. , Al-Zaabi R. , Al-Dousari M. , Al-Othman M. , Al-houti N. , Benamer N. , Hai Liu , Elsherif T. , Surjaatmadja J. , Elmofti M.
Published: December 2013

The Mauddud Formation in the Greater Burgan field is a thin carbonate reservoir with very low permeability but with moderate to good porosity and variable fracture density. The formation could be divided into three distinctive layers, based on the structural and digenetic complexities.

Production in Mauddud wells show rapid decline due to tight rock matrix (low permeability). This decline is associated with an increase in Gas-Oil Ratio (GOR) as reservoir pressure falls below the bubble point pressure near the wellbore. Horizontal wells were drilled in an attempt to develop the Mauddud Formation targeting sweet zone. Most of the wells were located in a relative structural high on the up-thrown blocks of the North and Eastern flank of the Greater Burgan field that had the highest likelihood of intersecting fractures. They are mostly adjoining the major faults. There are now around 40 wells drilled in Mauddud including horizontal and multilaterals, most of which became non-producers due to above reasons.

A study has been carried out to evaluate opportunities to revive these wells through available and new technologies in the industry. A detailed geological study incorporating all the available data was carried out initially. Wells were screened for stimulation by using various proven new technologies. Acid Frac, Stage Frac, near well bore SurgiFrac and Matrix Acid techniques have been applied with varying results. Advanced placement technique like distributed temperature profiling was used in some of the jobs.

This paper presents the details of the application of the above mentioned technologies, to the candidate wells and discusses the results. The success of some of these technologies opened up new opportunities for a new beginning to revive the closed wells completed in Mauddud Formation.
Capillary Pressure and Permeability Prediction in Carbonate Rocks - New Methods for Fractures Detection and Accurate Matrix Properties Prediction
Authors: Hulea I. N.
Published: December 2013

Carbonate rocks are known for their heterogeneity and petrophysical complexity. Core-measured permeability values can span orders of magnitude for a given porosity due to the diversity of pore types, as well as the propensity for carbonate rocks to contain (micro)fractures. Multimodal pore throat size distributions resulting from capillary pressure measurements are also an expression of the carbonate rock complexity. These complexities present challenges for accurate prediction of permeability and saturation, and the resulting uncertainties in reservoir models limit the reliability of fluid storage and flow predictions. Special issues arise when core porosity-permeability values are quality checked for low porosities (typically < 5 pu) as errors could have profound effects, especially in "tight" formations. Given these challenges, the goal for this work is a more accurate methodology for permeability prediction in carbonates using pore throat data to develop a quantitative technique that allows differentiation between matrix and fractures properties in porosity-permeability data. Our previous work showed that use of a normalized pore throat radius parameter yields a straight line relationship with permeability data over 6 orders of magnitude. Accuracy of the technique is validated when comparing predicted and measured permeability values from samples from diverse carbonate reservoirs from various periods of geologic time. An important result is that the method can define a valid permeability range, covering a wide range of pore types in carbonate rocks. Permeability values that exceed this valid range are most likely fracture-influenced (artificial or natural). Screening criteria for identification of fractured samples are independently validated by comparing unstressed and stressed permeability data. These newly developed methods are applied to conventional core data, leading to an improved accuracy of the modeled matrix properties.
Laboratory Screening of Corrosion Inhibitors for North Kuwait Oil Fields - A First Step in a Successful Corrosion Inhibition Treatment
Authors: Al-Hashemi Ahmed , Al-Azmi A. , Dabir M.
Published: December 2013

The selection of the appropriate corrosion inhibitor and the adequate injection rate is a important component of a successful corrosion inhibition program of a carbon steel used in an effluent water injection system in North Kuwait oil fields to prevent and control internal corrosion. Before proceeding to field trials, a comprehensive laboratory screening exercise of potential corrosion inhibitors was performed and used as a basis for selecting the best inhibitor(s). This work will highlight the laboratory testing experiments that were conducted to select the best performing corrosion inhibitors for North Kuwait oil Fields. The testing program will particularly consider for the critical operational parameters such as temperature, flow velocity/shear rate, brine chemistry and the range of chemicals injected in the water injection system. Such a wide range of parameters can be simulated using different laboratory testing experiments, including the wheel test, rotating cylinder autoclaves, bench top autoclaves. An illustration of a successful selection of a corrosion inhibitor for the water injection system will be illustrated as a case study.
Modeling of Shale-Swelling Behavior in Aqueous Drilling Fluids
Authors: Maghrabi Shadaab , Kulkarni Dhanashree , Teke Kushabhau , Kulkarni Sandeep D. , Jamison Dale
Published: December 2013

Shale swelling is a serious issue in water-based muds (WBM) as it may lead to stuck pipe, shale sloughing and decreased rate of penetration. Linear Swell Meter (LSM) testing is one of well-known laboratory tests used to characterize shale swelling. This paper describes how the time-dependent swelling response from LSM is modeled to extract characteristic parameters of swelling behavior. The study was performed for different shales with appreciable variation in smectite, illite and Cation Exchange Capacity (CEC). Swelling of these shales in WBM was investigated using different salt concentrations, mud weights and viscosities of the fluids.

Shale swelling as a function of time was modeled in a novel way as %S(t) = A *[f(B*t)+C*g(t)] where %S(t) represents swelling at time t. The equation was derived after combining first order kinetics term as f(B*t) with filtration loss term based as C*g(t). Thus, A represents saturation swelling volume, B represents first-order rate of swelling and C is filtrate loss rate parameter. The model fits well to experimental data with R2 > 0.97 for all shale-fluid combinations investigated which was used to extract the characteristic parameters.

Saturation swelling volume, A, increased with an increase in CEC of the shale. In addition, A decreased linearly till a critical salt concentration in fluid was reached and then flattened out with further increase in salt concentration. Such behavior conforms to osmotic transport of water through shale. It was observed that A was independent of mud weight and fluid viscosity; however B was observed to increase with a decrease in viscosity which may be interpreted as result of diffusion phenomena governing swelling rate. Filtrate loss rate parameter C was estimated to be between 0 and 1 in most of shale-fluid combinations studied. Information obtained from parameters A, B and C can allow us to optimize WBM formulations for shale that can save cost and time.
Case Study of H2S Dispersion at Exploratory Well Test using CFD Tools
Authors: Monjardim Vitor , Rocha Sandra , Piasseski Diogo
Published: December 2013

During the Well Test operation, critical information about the reservoir is acquired, allowing its characterization. In order to perform this activity and due to storage problems, all fluid produced at this exploratory phase is disposed to the atmosphere by burners. In some occasions the gas flare can go off, dispelling the gas without burning. It is called "cold flaring" and depending on the reservoir this might be a problem due the concentration of hydrogen sulphide (H2S) on the gas phase and environmental conditions, such as wind speed and direction. The H2S is a toxic and colorless gas, which is heavier than the air and soluble in both water and hydrocarbons. The limit of exposure is 10 ppm in atmosphere for an 8 work hours.

The aim of this work is to present and analyze different case studies, varying in line H2S concentration, flow rate, wind speed and wind direction, using computational fluid dynamics techniques. The software FLUENT® was used to run 15 different situations, with 48 simulations each, in order to determine safe conditions to flow the well.

Three different types of mesh with about 280000 cells each were used, depending on the wind direction. In each one of the simulations, the H2S plume with 10 ppm was analyzed and classified if it could be hazardous for the rig environment or not. As a result of this project, three charts were created showing the safe zones of operation depending on the gas and environmental conditions. After this study, several wind conditions that were considered dangerous are now safe, as example cases with high flow rate and low H2S ppm or low flow rate and high H2S ppm, reducing the down time due environmental conditions, ensuring that the work is being done in a safety zone.
Correlation of Porosity Uncertainty to Productive Reservoir Volume
Authors: Norman Charles Darrel
Published: December 2013

Monte Carlo simulations demonstrate that probabilistic models of hydrocarbon volumes should correlate the degree of porosity uncertainty to the productive volume of the reservoir. Assessments that fail to model the relationship between productive volume and porosity uncertainty may create unrealistic resource estimates and valuations.

The findings are applicable to conventional exploration prospects with significant uncertainty of productive reservoir volume, and to unconventional resource developments with high lateral variation in reservoir quality.

Probabilistic models of hydrocarbon volume include an estimate of porosity, defined by a probability density function such as a normal or lognormal distribution. The distribution models the uncertainty around the "average" porosity within the field. If a field is small, the productive volume represents a limited sampling of the reservoir. There is a possibility that the average porosity within the productive reservoir may be very high or very low. If the field is large, there is a greater chance that a high porosity in one portion of the field will be offset by a small porosity in another portion of the field, resulting in a narrow range of uncertainty around the average porosity. Probabilistic models that do not decrease the porosity range as reservoir volume increases may generate results in which a high porosity is applied to a large reservoir volume, resulting in resource volumes and economic valuations that are unrealistically high.

The solution lies in the use of multiple-segment models. If each segment represents a stratigraphic layer, or a portion of the potential productive area, and each segment is assigned the wide range of porosity appropriate for a small field, then increasing the number of productive segments will decrease the range of overall average porosity.

This paper clarifies the definition of porosity uncertainty in probabilistic models, reveals a relationship between porosity uncertainty and reservoir volume, and presents a method that will result in more realistic resource estimates and valuations.
High Resolution Diffraction Imaging of Small Scale Fractures Fields in Unconventional Shale Plays
Authors: Popovici Alexander Mihai , Sturzu Ioan , Musat Iulian , Tanushev Nick , Moser Tijmen
Published: December 2013

Summary

In 2000, shale gas represented just 1 percent of American natural gas supplies. Today, it is 30 percent and the percentage keeps increasing. The technology to drill and fracture the shale formations is now exported to the rest of the world, increasing the national oil and gas reserves in many other countries. The thickness of the shale formations is often just a few hundred feet, so new high-resolution technologies are needed to visualize the structure and the natural fracture distribution and orientation in these thin shale layers. Diffraction imaging can be used to complement the structural images produced by conventional processing - by generating an additional image volume of high resolution unconformities - such as small scale faults, pinch-outs, or salt flanks.
A Case Study of Effective Immiscible Hydrocarbon Injection for Enhancing Oil Recovery in a Mature Oil Field
Authors: Pearce Adrian , Madathil Asok , Blondeau Christophe
Published: December 2013

Total has operated an oil field, offshore Abu Dhabi, since 1972 and, after nearly 40 years of production, the major Lower Jurassic reservoir, has one of the highest oil recovery factors in the UAE owing to a strong aquifer pressure support and a successful tertiary recovery process. After 16 years of non-miscible gas injection, this EOR technique has significantly improved oil recovery and also brought valuable lessons.

The purpose of this paper is to present the practical challenges encountered and the solutions developed to address the full field tertiary gas injection scheme. Around 28% of the production since field-wide application of the EOR technique has been attributed to this immiscible process.

Gas injection dynamic behavior is much more sensitive to reservoir heterogeneity than water injection. A more detailed geological and reservoir model was required along with a gas tracer campaign to model properly the well response to the gas injection. Gravity appears to be the main factor controlling the macroscopic sweep efficiency.

As the full field efficiency is highly dependent on the gas management strategy, an extensive monitoring is required to maximize tertiary oil gains and avoid surface bottlenecking. An analytical methodology was developed to forecast oil gains and to allocate the gas in the best sectors.

From the beginning of the project, incremental oil gains are in line with the initial objective and have confirmed the added value of immiscible tertiary gas injection in a mature field.

The gas injection will continue in order to pursue the objective to maximize the ultimate recovery of this field by implementing innovative technical solutions. This requires constant vigilance, sound day-to-day reservoir and well management as well as prioritizing tasks with operations’ staff on a mature platform with competing processes.
Steering with the Multifunction LWD Tool Achieves Optimum Results in High Structural Uncertainty Field in Egypt
Authors: Swire P. , Badr Y. , Ramadan Z. J. , Khattab T. , Siam M. M. , Dolan J. T. , Samir E. , Khattab A.
Published: December 2013

The high structural uncertainty present in a field in Egypt required special logging-while-drilling (LWD) measurement specifications to achieve economically satisfying production results. East Zeit Oil Company (Zeitco) was targeting an oil-bearing sandstone reservoir that is characterized by the presence of subseismic faults and high structural uncertainty. This uncertainty ranges from 6° to 23° in structure dip, which makes drilling successful horizontal wells in this reservoir challenging. A well with a horizontal penetration envelope from a minimum 500 ft measured depth (MD) to an optimum 1,600 ft MD was planned for this reservoir to make the well economic. Steering in such a challenging reservoir required having realtime measurements as close as possible to the bit to make the required real-time decisions. A real-time density image and with other azimuthal data were the primary measurements used in steering this horizontal well. Being used with a rotary steerable tool, the multifunction LWD tool provided density image at only 39 ft behind the bit, which was crucial for the success of the well. The well was successfully drilled with 100% exposure inside the sandstone reservoir with 1,532 ft MD horizontal penetration. In addition, well testing results indicated a natural flow of 2,000 BOPD, which made this well the highest oil producer in the field.
Construction of Bulk Handling Facilities for Production Chemicals in S&EK, WK and NK Areas
Authors: Awan Mukhtar A. , Al-Khaledi Sadoun
Published: December 2013

Production chemicals are primarily used to treat crude oil to its sale specifications, to minimize process problems, and to treat produced water to meet regulatory guidelines for disposal or injection. Voluminous quantities of various chemicals are used in production operations - Company uses more than 50,000 drums (55 USG standard drums) per year at different locations throughout the field areas. Transferring drums from stores to the facilities, chemicals loading from drums to the tanks, spillages and disposing-off empty drums have been causing numerous operational, health, safety and environmental concerns. Therefore, in line with Company’s policies of enhancing it’s operational & HSE performance, the Company decided huge capital investment (KD 16 Million) for constructing modernized facilities for bulk handling of the production chemicals.

This paper outlines the facilities and associated support systems for bulk handling of the chemicals, eliminating use of the conventional chemical drums (55 USG standard drums). The facilities comprise of the Primary Chemical Storage Facility consisting of ten (10) storage tanks for receiving the chemicals in Road Tankers, and subsequent distribution by specialized road tankers (loading arm conforming to API-RP 1004) to the Secondary Storage Facilities in the Gathering Centers (20 Nos.) located in different field areas. The Primary Storage Facility is provided with loading & unloading pumps, ethernet based Terminal Automation System (TAS), utilities, control room & offices, fire-fighting, safety & public address systems, etc. The Secondary Storage Facilities have been provided at the Gathering Centers, with filling connections, instrumentation/controls, pumping facilities, etc. to the Day Tanks.

Oil Companies normally outsource chemicals handling activities. But our Company decided to build its own facilities - unique of its kind. Knowing that many oil majors in the region do not possess bulk handling facilities of this magnitude and configuration, our facilities could be a model for others. Company carried out extensive work prior to the project, in examining options, payment procedures, inventories controls, tankers selection, safety systems, waste management, etc.

Construction of bulk handling facilities is a landmark that enhances Company’s HSE & operational performance, improves inventories & quality controls, eliminates manual handling, and storage/losses problems.
Application of Different De-Convolution Methods in Well Test Analysis of One Iranian Naturally Fractured Reservoir
Authors: kamalipour Meisam , Shahrabadi Abbas
Published: December 2013

In reality the rate of a production well is not constant and varies in time so the producing responses would be noisy. De-convolution is a method of converting a variable rate distorted pressure profile into the pressure profile for an equivalent constant rate production sequence. There are two methods used for de-convolving distorted pressure data: Beta De-convolution and material balance de-convolution methods. The application of both methods was tested in well test analysis of a naturally fractured reservoir. The end of well bore storage was estimated by both methods, and then the reservoir data were analyzed by well testing software. The calculated permeability, interaction coefficient and storativity ratio are different in both approaches. The comparison of data shows that the material balance method predicts the pressure response better and is suggested for applying in field cases.
Exception Based Monitoring As A Tool For Real-time Optimisation: How To Prioritise Well Interventions in Very Large Oilfields
Authors: Crockett Brian J.
Published: December 2013

PROBLEM STATEMENT

Many assets have oilfields with more than a thousand producing wells to monitor, which means that the well analysts find that they can only concentrate on the high producers. The result is that other wells drift out of their operating envelop and in some cases shutdown. With real-time data from tens of thousands of indicators flooding in, the Production team need an exception based monitoring (EBM) system which alerts them when a well is indicating an anomaly, displays it in a prioritised and manageable manner and provides an automated workflow for resolving the issue.

OBJECTIVES

To demonstrate the need for greater visibility and a method for providing a web based portal which can be used to compare real-time data with a set of operating envelope parameters for wells and facilities and detect anomalies as alerts. Show how this was achieved in Oman, Nigeria and the UK.

METHOD Highlight the problems of handling too much data Show how alerts can be sorted, analysed and prioritised automatically Explain how acknowledgement of these anomalies can activate an automated workflow Clarify how optimisations are tracked and escalated

RESULTS The initial deployment of the system produced more than expected anomalies Automatic sorting of the alerts prevented excessive emails being generated Alerts can be grouped geographically Increase in Optimisations and Production

APPLICATIONS

This approach can be used for wells, facilities and data quality.

INNOVATIONS Monitor by exception Prioritise anomalies automatically Provide an automated workflow to track optimisations. It works with Collaborative Work Environments to improve capability

CONCLUSIONS

The deployment of an EBM system gives complete visibility of facilities permitting production teams to focus on optimising critical wells while ensuring that other facilities do not drift towards shutdown.
Implementation of Integrated and Practical Workflow for Fluid Substitution to Improve Seismic Inversion Results: a Case Study from a Carbonate Field in the UAE
Authors: Haggag Mostafa , Chacko Soman , Baloushi Mariam Al , Arafat Mohamed
Published: December 2013

The field under study is structurally and stratigraphically complex, which increases the uncertainties associated with field development. To optimize reservoir characterization using seismic data, seismic inversion (Deterministic, Stochastic and Simultaneous) was planned to be performed using the 3D seismic data covering the field. Given that well log data provide constraints and calibration in the inversion workflow, their quality has a direct impact on the robustness of inversion results. This paper focuses on corrections made to sonic and density log data to make them suitable for seismic inversion.

Sonic and density logs have shallow depths of investigation and are affected by borehole irregularity and filtrate invasion. Errors due to borehole irregularity in the section overlying the reservoir impact two key stages of the inversion process: wavelet extraction using well-seismic ties, and construction of the low frequency or a priori model. Invasion within the reservoir impacts the accuracy of porosities obtained from seismic impedance data. Typically porosity estimation is done using a regression relationship between porosity and acoustic impedance derived from well log measurements. The log impedance data (both velocity and density) are affected by saturation changes related to filtrate invasion which must be corrected for, to obtain a reliable porosity-impedance relationship.

A robust and practical workflow to address log quality issues begins with log data quality QC: identifying zones with missing logs or borehole affected log readings. Shear sonic logs are unavailable for many wells, which limits their use for Simultaneous inversion, and for invasion correction using a rock physics model. We constructed shear sonic logs from compressional sonic logs using a rigorous, iterative process. Gassmann's equation was then used to correct for filtrate invasion effects. Invasion effects were found to change impedance values within reservoir intervals by as much as12 %, which has implications for 4-D seismic monitoring of the reservoir.
Hybrid Drill Bit Combining Fixed-Cutter and Roller-Cone Elements Improves Drilling Performance in Challenging Application in the Western Desert
Authors: Ismail Ahmed , Hussein Sameh , Eckstrom Darren , Shawkat Mahmoud , Hughes Baker , Kamel Osama , Staal BJ , Ibrahim Abd El
Published: December 2013

The application of hybrid bits saves the operator drilling time by out-drilling conventional roller-cone and fixed-cutter bits in difficult, dense, tough and interbedded intervals. These intervals comprise interbedded sandstone, limestone, and siltstone down to depth of 12,500 to 13,500 ft. Operators who drilled these overbalanced wells typically used conventional roller-cone and fixed-cutter bits, depending on the area of the play. The roller-cone bits consistently drilled the entire interval, yet achieved slow penetration rates due to the lack of available weight. Fixed-cutter bits have been tested to achieve higher penetration rates. They drill faster than roller-cone bits with the available weight on bit but with higher drilling torque, close to the rig limitation. Fixed-cutter bits also experience dynamic dysfunctions that prematurely damage the bits, making it difficult to complete the entire interval.

Extensive research, testing, and development have produced a hybrid bit that combines roller-cone and fixed-cutter elements to address these major challenges. The fixed-cutter elements make the bit more aggressive and provide higher penetration rates at low weight on bit. The roller-cone cutting elements drill through the harder part of the interbedded formation with much lower torque oscillations, making it easier to achieve the directional requirements, and reduce dynamic dysfunctions, improving the reliability of the bottomhole assembly and a better dull condition of the drill bit.

This paper will present analysis of drilling data from the field to provide a detailed description of the operational challenges in this application by comparing the performance of roller-cone, fixed-cutter, and hybrid bits. After describing the planning and operational execution of drilling an 8.5-in. hole section with a hybrid bit in this challenging application, the paper concludes with a discussion of the technical and economical benefits and potential of this new technology.
Wireline Borehole Images–LWD Well Placement Integration to Determine Faults in Awali Field, Bahrain
Authors: Sultan Hassan , Alhashimi Lana , Juandi Dedi , Al-Alqum Wael , Al-Hamad Nasser
Published: December 2013

The Awali field is a mature carbonate oil field in Bahrain. It is a giant gentle limb of anticline compartmentalized by numerous normal faults. The reservoir is intersected by normal faults that create half-graben reservoirs. Characterizing these faults through borehole data is necessary to understand the reservoir compartmentalization and improve the geologic model, which was built from seismic data of poor vertical resolution.

Fault structure was characterized by the deep directional resistivity of a logging-while-drilling (LWD) tool used to geosteer horizontal wells through faulted zones. The LWD tool detected the faults, determined their throw and estimated its extent, and mapped the bed boundaries up and down within its depth of investigation. With this information, engineers were able to place wells over horizontal sections ranging from 1,000–3,500 ft [305–1,067 m] MD within the target zone and stay just 4–14ft [1.2–4.3 m] below the roof (i.e. the top of the Kharaib carbonate reservoir).

The high-resolution wireline borehole image logs recorded after the well reached TD provided further confirmation of fault presence and strike and dip angle. On borehole image logs, normally the faults are indicated by fracture association and drag pattern on nearby structural bedding dips or by abrupt facies or textural changes. Most faults in the Awali field have NW–SE trends with high dip angle; they are considered as a normal fault regime forming the graben and half-graben reservoir traps. Combining the complementary LWD well-placement results and high-resolution borehole image log interpretation enabled us to determine the fault type and its orientation.
Modular Design for Low Cost Minimum Facilities Platforms
Authors: Nicholson Graham , Helle Yann
Published: December 2013

To meet the ever increasing demands for cost and schedule efficiencies in the development of marginal fields it has become necessary to streamline the design process for platforms and employ lean engineering techniques. The introduction of minimum facilities platforms in conjunction with existing infrastructure or MOPUs has enabled operators to develop marginal assets without the large capital expenditure associated with new permanent production facilities. It has been shown that minimum facilities platforms can be produced at relatively low cost and designed to suit specific fabrication and installation requirements. As a result the popularity of minimum facilities platforms has grown and has heralded a new wave of flexible design solutions for a range of applications and water depths.

The technical challenges involved in the design of minimum facilities platforms include structural strength and fatigue resistance as well as meeting installation constraints. A typical conductor supported minimum facilities platform incorporates topside, conductor legs and a subsea template. Although the external platform loading is dependent on unique local water depth and environmental conditions, the overall platform response is primarily governed in only three ways; opside load, conductor size, conductor free-span. Through the use of pre-qualified designs and methodologies it is therefore possible to quickly develop a range of structural solutions to suit a particular application. This paper explores the potential for a modular approach to minimum facilities platform design with a focus on reducing the cost and schedule for development, fabrication and installation.
Analytical and Numerical Modeling of Tracer Flow in Oil Reservoirs Containing High Permeability Streaks
Authors: Kocabas Ibrahim , Maier Friedrich
Published: December 2013

Tracer testing is a powerful tool for reservoir description and evaluation at every stage of the productive life of a reservoir. In this work, we present an analytical and numerical model for the transport of tracer in oil reservoirs containing a high permeability streak. The new analytical model is aimed to aid in the interpretation of tracer tests, provide a better insight into the mechanisms of tracer/EOR fluids transport, understand the role of input parameters, and provide a useful benchmark for numerical simulators. The model is validated by a numerical simulator COMSOL Multiphysics 4.3 which employs finite element technique in its ‘Subsurface Flow" module.

The new analytical model is distinguished with its ability to account for finite longitudinal and transversal tracer dispersions in the high permeability streak and the tracer loss into the bounding low permeability layers. Thus, being possibly the most comprehensive exact analytical unsteady two dimensional tracer transport model, it exhibits the roles of both boundary conditions and fluid mechanics controls simultaneously. Intuitively, one would expect that the coupled one dimensional analytical solutions may be appropriate for the systems with a large aspect ratio defined as the ratio of the length of high permeability zone to its half-width. In this work, however, we demonstrate that the parameter which controls the applicability of one dimensional models is the square root of ratio of the two characteristic times of longitudinal and transverse dispersion. While we have validated the analytical solution with a finite element simulator, the analytical solution in turn provided an advanced benchmark free of numerical dispersion and unphysical oscillations in two-dimensional domains for numerical models.

The nonlinear regression programs coded in MATLAB are employed to interpret the tracer return profiles, and hence, to be able to estimate the models parameters along with related confidence intervals.
Energy Conservation Through Flare Reduction
Authors: Dhahli Mohammed Al , Proot Michael , Rodoljub Mihajlov
Published: December 2013

Gas extracted from crude oil is often exported as sales gas. In Petroleum Development Oman (PDO), the story is different. The demand for natural gas is increasing with expansion of Enhanced Oil Recovery (EOR) projects within PDO (for example, miscible gas injection) and increased end user consumption across Oman. Realizing the need for gas conservation, PDO has given more focus on flare reduction projects reflecting this in the business planning.

Birba Gathering Station (BGS) is the first high sour facility in PDO where associated gas is injected for pressure maintenance purposes. The station consists of number of compression units where the gas is compressed to ~470 bar before it is injected into the reservoir. Flaring in BGS has traditionally exceeded 300 kSm3/d. To adhere to a practical minimum flaring in PDO, a flare reduction project for BGS was initiated.

As a first step, the main causes of the flaring in BGS were identified by analyzing actual field data (i.e. history trends, trip reports, etc.) and highlighted the critical role of the compressors uptime. Once the critical flaring contributors were identified, a number of concepts emerged how flaring can be reduced by improving the compressor availability and/or sparing. A technical and economical evaluation was performed to identify the ALARP (As Low As Reasonablely Practical) option which is now selected for implementation.

In summary, the paper will explain in detail the systematic approach that was used to identify the root cause of the flaring in Birba Gathering Station using the trip data. Subsequently, it will discuss the different concept options and the evaluation of the options against the project criteria. The discussion will include the economic model used and the selection of the preferred option.
Evaluating Flow Contributions and Enhancing the Design of Smart Well Completions
Authors: Al-Muailu H. A. , Al-Suwailem M. , Aldawsari S.
Published: December 2013

Over 70% of an onshore Saudi Arabian field maximum reservoir contact labeled wells are equipped with smart well completions; mainly to control undesirable effluent production. Several optimization best practices are routinely conducted through extensive sophisticated rate testing operations that are combined with the utilization of deployed intelligent devices. This entails the optimal setting of ICVs for ideal production and restriction of high gas or water laterals to determine their productivity indexes (PIs) and revive dead laterals.

This paper documents the utilization of Netool in evaluating smart well contributions. A case study will be thoroughly discussed whereby a smart trilateral producer with flow meter log results exhibits unexpected flow contributions. Netool was used to evaluate the flow meter log to optimize the inflow control valve (ICV) settings. The model was validated with the actual flow rates of individual laterals. Moreover, Netool was utilized in evaluating and analyzing the current completion practices in terms of the spacing between the ICVs and the optimum blank pipe size.

The results of the model contradict the flow meter log results. Several, rate tests were completed in the well resulting in more confidence in the model results. New proposed ICV settings balanced the flow rate and the pressure draw down between the three laterals. The paper will show that the greater the increase in the distance between the ICVs the greater the variance in the laterals contribution. The optimum spacing providing more balanced flow contribution came to be 300 ft. Sensitivity analysis was conducted over the blank pipe sizes, proving that a reduction of 40% pressure drop can be accomplished through having larger blank pipe between the ICVs from 3 ½" to 4½".
The Impact of Heat Flow Variations in Shale Gas Evaluation: A Haynesville Shale Case Study
Authors: Amer Aimen , di Primio Rolando , Ondrak Robert , Unnithan Vikram
Published: December 2013

The Upper Jurassic Haynesville Shale play covers an area extending through East Texas, northwest Louisiana and parts of southwest Arkansas. The true potential of this play as an unconventional play was largely unknown. Only after gas prices increased during the last decade oil companies started to see the Haynesville Shale as an economic shale gas play, despite its great depths of over 3000m. At present gas prices the Haynesville Shale is due to its depth once again of only marginal interest, however, in order to be prepared for renewed interest a fundamental understanding of the processes and timing controlling shale gas prospectivity is required.

In order to understand the variables of this unconventional play, we have identified the heat flow history as a critical control. Heat flow values and evolution through time can impact the critical timing of gas generation, secondary cracking of oil to gas, and oil and gas generation critical moments.

Using state of the art basin modeling software, a reconstruction of the heat flow history was performed. Predicted formation temperatures were calibrated against temperature data collected from 1644 wells drilled over the play.

Paleo-temperature evolution was calibrated against vitrinite reflectance data collected from 26 wells. Laboratory Rock-Eval analyses were utilized to assist in this study over 6 wells.

The area has been subjected to three major tectonic uplift events. After various simulation iterations we conclude that the heat flow increased slightly with each uplift event. This suggests that the uplift was accompanied by heat flow increase indicating a likely igneous control, which had a large impact on the heat flow history within the area. Such understanding proves to be vital in order to perform accurate hydrocarbon resource assessments.
Innovative Single Phase Tank Technology for In-Situ Sample Validation Enhances Fluid Sampling Integrity
Authors: Sanchez Francisco Galvan
Published: December 2013

Millions of dollars are spent each year drilling in deepwater areas to prove the presence of hydrocarbons. Wireline formation testers (WFT) are able to capture and retrieve multiple, discreet hydrocarbon fluid samples at in-situ conditions. Once the sample bottles are retrieved at the surface, expeditious sample validation is critical because it provides certainty on sample type and quality. The typical process for wellsite sample validation is often very expensive and risky because it requires a full laboratory restoration apparatus, a portable lab, and trained personnel to handle high-pressure samples —often under unfavorable conditions.

The Advanced Optical Cylinder (AOC) is the latest development in single-phase sampling technology by Baker Hughes. The AOC sample chamber eliminates the high risk and costs associated with sample quality validation in the field and provide clients with very valuable and timely fluid sample data. The AOC is a nitrogen-charged sample tank that provides pressure compensation to retrieve single-phase samples; it incorporates visible-near infrared (Vis-NIR) technology to obtain spectroscopic measurements of the sample within the tank. Capturing a single-phase sample is very important because the accuracy of reservoir fluid samples provides critical information needed for optimal completion and production design. Vis-NIR spectroscopy is a well-established tool used in downhole fluid analysis that provides critical information such as fluid type, sample purity and PVT properties. With the AOC, it is now possible to verify the visible-near-infrared spectra of the captured crude oil or gas sample as soon as the tanks reach the surface, and without the need for sample transfer. Benefits include avoiding lengthy waiting periods for PVT laboratory analysis, ensuring quality samples, and enhancing critical reservoir development decisions.

The AOC provides the best method for non-invasive sample validation of the captured formation fluid sample, using a high-resolution spectrometer that easily connects to the tank (to capture detailed visible and NIR spectra of the pressurized fluid sample). The spectrum is compared to fluid analysis data acquired during WFT sampling; further VIS-NIR spectra analysis j determines contamination, GOR, bubble point, and API gravity.

Field examples are used to demonstrate the application and benefits of in-situ sample validation using the AOC.
Optimization Of Drilling Fluid Rheological And Fluid Loss Properties Utilizing PHPA Polymer
Authors: Kelessidis Vassilios C. , Zografou Maria , Chatzistamou Vassiliki
Published: December 2013

Drilling fluids with bentonite can often cause major problems such as flocculation, loss of rheology control and excessive friction due to high clay concentration. Polymers can mitigate such problems, but all these come with much higher costs. Partially hydrolyzed polyacrylamide (PHPA) polymers are used as additives to bentonite water based fluids to stabilize shales and in HTHP applications because of better thermal stability (PHPA). It also acts as coating on cuttings preventing agglomeration minimizing fluid loss and aiding cuttings transport. There is not much published information about PHPA optimum concentration and its mode of action and we aim to identifying these and we attempt to explain the effectiveness for achieving better design of drilling fluids.

Four bentonite (2%, 3%, 4%, 5%) and five polymer (PHPA) concentrations (0.05%, 0.1%, 0.3%. 0.5%, 0.7%) were used. The rheological behavior was described very well by the Herschel-Bulkley model. PHPA addition resulted in increase of apparent viscosity, large decrease of the yield stress and in great reduction of the fluid loss and models are presented for such behavior. The morphology of the filter cakes was investigated using Scanning Electron Microscopy in order to understand the adsorption of the polymer onto the clay particles. We try to explain the effectiveness of polymer addition and its mode of action, which further enhances our understanding of the polymer-clay interaction.

This work aids into formulating better water-based fluids for such applications using optimal polymer concentrations. Better understanding of the mode of interaction of the PHPA additive with clay particles in drilling fluids has been achieved by in-depth analysis of the effect of various concentrations on rheological and filtration properties of drilling fluids. This allows industry to work with optimal PHPA concentrations for more efficient drilling.
Integrated Workflow to Evaluate and Understand Well Performance in Multi Layer Mature Gas Reservoirs, Bahrain Case Study
Authors: Eissa M. , Kumar A. , Zaouali Z. , Chaabouni H. , Al-Ghadbhan H. , Kadhim F.
Published: December 2013

Natural gas is the primary source of energy in Bahrain, and the Khuff reservoir is the main supplier for this gas4. The Khuff reservoir, which was discovered in 1948, is composed of four limestone layers (K0, K1, K2, and K3) separated by tight limestone and anhydrite beds that can act as permeability buffers in some areas of the reservoir.

In such a mature carbonate gas reservoir as the Khuff, managing and optimizing the performance of wells represents a challenge for the reservoir and production engineers because of the reservoir heterogeneity created by dissolution process which induced good porosity and permeability zones within a lower quality matrix rock; differential depletion, which occurs because reservoir heterogeneity creates a pressure difference between layers; and the commingle production as Khuff wells are completed comingled using either openhole or perforated completion.

An integrated workflow applied to Khuff wells helped to understand the well performance and to optimize the workover activities. The process integrates the geological information, openhole data, multirate production logging test data, time-lapse corrosion logs, multilayer transient testing, and nodal analysis and is used to determine the remedial job that is required to achieve the most favorable well performance.

The process was applied to one of the Khuff wells that was originally completed as K2 producer and then K1 and K0 were added in double casing using a small gun size because of completion limitations. The well performance after adding K1 and K0 was below expectation, and conclusion was made that the new perforations are not performing as been expected because of insufficient formation penetration. Thus, proposed remedial actions were to reperforate the K0 and K1 intervals using a bigger gun size and then stimulate them. However, before starting this costly operation, the integrated workflow process was used to assess the need for this workover operation. The integrated evaluation showed a different conclusion, which led to different workover plan, thus saving the cost of a more expensive workover operation.