bluuebunny/crossref_metadata_2025 huggingface dataset:
Permeability and Water Saturation Distribution by Lithologic Facies and Hydraulic Units: A Reservoir Simulation Case Study
Authors: Shenawi Shamsuddin H. , White Jerry P. , Elrafie Emad A. , El-Kilany Khaled A.
Published: December 2007

In a large clastic reservoir of Saudi Arabia, rock typing by rock-quality-index (RQI) and flow-zone-indicator (FZI) proved to be an effective technique to develop porosity-permeability transforms for 8 lithologic facies in a reservoir model. Moreover, capillary pressure and relative permeability curves could be grouped into defined rock types as well. This technique provided an effective tool to distribute permeability, initial water saturation, relative permeability, and residual oil saturation per lithologic facie.

Conventional core porosity and permeability data were used to determine FZI for each core. The FZI was manipulated mathematically to group into hydraulic units (HU) in distinct integers. Each HU was then correlated to corresponding defined lithologic facies. The resulted porosity-permeability transform for each facie was applied to distribute permeability in the reservoir model. Relative permeability and capillary pressure curves also clustered together in corresponding HUs. Confidence levels in distribution of initial water saturation and residual oil saturations were increased due to this HU rock typing.

Series of J function and relative permeability curves for 8 facies were applied in the 1.4 million gridblocks reservoir simulation model. Distributed permeability and initial water saturations were validated against pressure transient analyses, core and well log data, and proved to be in excellent agreements. As a result, the uncertainty associated with petrophysical parameters was greatly reduced. The simulation model developed with the combination of HU rock typing and lithologic facies provided a higher history matching statistic (~70%) for 500 wells in a couple of weeks using assisted history matching method where facies-based petrophysical and aquifer parameters were globally modified in very narrow ranges.

This paper presents through a case study the methodology applied for generating permeability and water saturation distribution by lithologic facies and hydraulic units and its impact on simulation history match and future prediction.
Long-Term Evaluation of Low-Density Cement: Laboratory Studies and Field Application
Authors: Al-Yami A. S. , Nasr-El-Din H. A. , Al-Saleh S. H. , Al-Humaidi A. , Miller C. , Al-Yami H. , El-Marsafawi Y.
Published: December 2007

Cementing a string in one stage is a challenging task, especially in the presence of weak formations. Cement slurry losses during placement is highly possible in S-1 (sandstone) and S-2 (carbonate) formations, if the equivalent circulating density (ECD) exceeds 11 lb/gal during placement. A conventional method to overcome this challenge is to use multi-stage cementing by setting the stage tool above the loss circulation zone. However, the success of this tool is limited. A second method is to use low density cement.

In this study, we present extensive lab work evaluation of a low density cement system based on the use of hollow microspheres at field conditions. The tests included shrinkage, compressive strength development, porosity, gas and brine permeability. Data generated during three months supported the use the cement examined.

The hollow microspheres cement was applied in several gas wells. The technical objective of the cement job was to achieve zonal isolation across the weak S-1 & S-2 formations. The operation objective was to cement the casing to the surface in one stage without using stage tools.

This paper will discuss case histories that include job design, execution, and evaluation of the hollow microspheres cement. Field treatments were conducted without encountering any operational problems. The treatment was successful and maintained isolation for more than three years which confirmed the effectiveness of this cement system.
Expert Determination in International oil & Gas Disputes: The Impact of Lack of Harmonization in Reserves Classifications Systems and Uncertainty in Reserves Estimates
Authors: Stultz-Karim S. P.
Published: December 2007

The resolution of international oil and gas commercial disputes in regards to reserves determination is frequently relegated to the final and binding determination of an expert. Although expert determination (ED) is often the preferred dispute resolution method because of the technical nature of the issues and the appeal of a more timely decision than international arbitration, expert determination does not enjoy the same level of recognition or enforceability as an international arbitral award. Also, in the particular technical dispute area of reserves expert redetermination, lack of harmonization of classification systems in reserves estimates brings additional issues to consider in international oil and gas commercial disputes.

This paper is a review of current literature in the areas of expert determination in international oil and gas technical disputes, reserves classifications utilized throughout the international industry and uncertainty in reserves estimates. It will focus on the uncertainties which arise with the use of expert determination in international oil and gas disputes. These uncertainties relate to the immaturity of international law in the area of expert determination and to the lack of harmonization of reserves classification in the international oil and gas industry.

The uncertainty of the factors related to expert determination in the resolution of international oil and gas reserves disputes, however, does not mitigate the effectiveness of this dispute resolution method. Rather, with knowledge of the uncertainties, expert determination may be utilized more effectively to resolve the financially weighty reserves disputes of international oil and gas agreements.
Applications of Streaming Potential Transient Tests to Electrokinetic Characterization of Oil Reservoirs
Authors: Alkafeef Saad F. , Alajmi Nab M. , Alajmi Abdullah F.
Published: December 2007

Electrokinetic techniques have proven to be a valuable tool in providing direct information on charge solid/liquid interface. Today, oil industrial companies are looking into electrokinetic techniques with great interest, in order to describe the oil reservoir physics occurring in and near the well bore during production. This paper introduces a new method, which uses streaming potential transient testing to characterize the electrokinetic properties of oil reservoirs. Streaming potential exists in the movement of part of electrical double layers from the charged pore surfaces when fluid flow is induced by an applied pressure gradient. A fully computerized high pressure and high temperature core holder device is utilized to simultaneously measure streaming potential and pressure transient tests. The time behavior of the transient steaming potential is identical to that of fluid pressure when laminar flow is maintained. The transient streaming potential data is a useful quantity for determining the electrokinetic (zeta) potential values produced at the reservoir rock/fluid interface, and is considered an important electrokinetic characteristic that can play a role in reservoir rock properties. In low conductivity liquids, such as petroleum fluids, the surface conduction of reservoir rocks will cause errors in streaming potential measurements and therefore any derived electrokinetic potentials are also affected. The latter is corrected by determining the total electric conductivity of reservoir rocks, including the surface conductivity. The compressibility of reservoir fluid has been shown to affect streaming potential measurements and the results of electrokinetic potentials. We believe that this work is an important addition to the hydraulic and electrokinetic characterizations of oil reservoirs.
Applications of Mechanical External Casing Packers
Authors: Armenta Miguel , Al-Ghamdi Ali , Al-Hajji Ali
Published: December 2007

Field cases presented on this paper explain applications of Mechanical External Casing Packer (MECP) solving zonal isolation problems on openhole horizontal wells in Saudi Aramco. MECP is essentially a hybrid between existing cased-hole conventional packer and inflatable External Casing Packer (ECP). MECP is different than ECP in the mechanism energizing the sealing element. The packer is run as an integral part of the casing string to provide a seal between the casing and wellbore. Saudi Aramco has successfully used MECP controlling water production, isolating fractured open-hole sections, sealing casing shoe with leaking problem, and compartmenting openhole horizontal section.

Included in this paper are four different field cases for openhole zonal isolation with MECP on horizontal wells. Each field case presents a particular application for the MECP. Technical data including well configuration and casing string are included in the paper. Field operations and lesson learned from each application are also presented in this paper.

MECP has been successfully used for zonal isolation on openhole horizontal wells. Depending on the particular application, MECP can be run in combination with blank and/or screened pipe. Hole cleaning and wellbore conditions are factors affecting MECP placement.

The knowledge provided in the paper can be applied to solving zonal isolation problems on openhole horizontal sections with different rock and fluid properties. The significance of this paper is that it presents actual field experiences and lessons learned for MECP applications. Furthermore, recommended field operations for successfully placing MECP on the well are also included in this paper.
Waste Subsurface Injection: Pressure Injection and Decline Analysis
Authors: Shokanov T. A. , Nolte K. G. , Fragachan F. E. , Ovalle A. , Geehan T.
Published: December 2007

The economic impact of missing production targets represents high risks that demand engineering based and sound processes to ensure injection assurance.

This paper describes the results of pressure analysis conducted in injection wells, successfully utilized for Cuttings Re-Injection (CRI) and disposal of produced water because of a close monitoring of pressure injection and decline, in spite of the risky conditions. Abnormal pressure increases, and restrictions observed during injection were mitigated via engineered diagnostics.

This paper also describes the interpretation and methodology implemented to maintain safe injection assurance via regular pressure analysis until pressures reached values above overburden indicating need for associated risk assessment, including potential breach to the surface. Characterizing the disposal domain using injections monitoring and in-depth pressure analysis is a major step to enhance mitigation of waste environmental protection risks posed by CRI. Past interpretations of waste domain, appear to be in conflict with rock mechanics, hydraulic fracturing and general physics principles.
Casing-Drilling Step Improvement: PDC Successfully Drills Out Casing Bit and Finishes Hole Section at Lowest Cost
Authors: Johnstone Ian , Chomley Alistair , Cernev Gheorghe , Hoq Mahbub , Atherton Geoff , Cornel Santos Simon , Jacobs Martin , Christensen Hughes
Published: December 2007

Recent technological advances are driving casing drilling from a niche market into the mainstream environment. Improved connections, tubulars, advances in rig technology and pipe handling have enabled operators to consider drilling with casing/liner as an option on many new wells. In Cooper Basin, onshore Australia the need to further reduce drilling expenses in area continues to push the technology forward.

At the outset of the project, the operator's main goal was to improve drilling efficiencies with the aim of drilling more wells per rig per year. The secondary objective was to reduce costs and make the wells more economically feasible. To address these challenges, the service company recommended a specialized casing bit manufactured from a specialized steel alloy that allows technicians to braze PDC cutters directly to the one-piece bit ensuring a robust cutting structure capable of efficiently drilling new formation as well as reaming existing hole while drilling casing in place. They also recommended a new-style drill out PDC to drill through the casing bit and continue drilling formation without tripping for a new bit.

The new 6–3/4" drill out PDC bit (XDO) was run with outstanding results. It demonstrated the ability to drill through the casing drilling shoe and drilled ahead 6,000ft to TD in one run. The XDO held inclination at high WOB and did not ball up. The successful trail proves the feasibility of this technology in a full scale casing drilling application, moving the application one step closer to reality. The bit company plans to redesign the XDO to improve performance in the drill out and through the softer formations out of the shoe.

The authors will make cost comparisons with offset wells drilled with conventional drilling systems. They will also focus on lessons learned through using this new technology.
Assuring Stability in Extended-Reach Wells—Analyses, Practices, and Mitigations
Authors: Willson Stephen M. , Edwards Stephen T. , Crook Anthony , Bere Adam , Moos Daniel , Peska Pavel , Last Nigel
Published: December 2007

Whilst the step-out lengths of proposed ERD wells are becoming more and more challenging, wellbore stability assurance technologies - both in the pre-planning and execution phases - are developing at an equal pace. In this paper we describe several new developments in theoretical understanding and predictive capability of rock failure surrounding wells drilled at high-angle to bedding that are required to solve the problems encountered in these challenging environments. Rig-site processes for the integration of this new understanding with real-time diagnostic measurement and monitoring provide the means to deliver borehole stability assurance for ERD wells drilled in the most challenging environments.
First Full Field Steam Injection in a Fractured Carbonate at Qarn Alam, Oman
Authors: Penney R. , Baqi Al Lawati S. , Hinai R. , Van Ravesteijn O. , Rawnsley K. , Putra P. , Geneau M. , Ikwumonu A. , Habsi M. , Harrasy H.
Published: December 2007

Gas Oil Gravity Drainage (GOGD) of the Qarn Alam fractured low permeability carbonate reservoir is being enhanced by steam injection in the world's first full field development carbonate thermal development. Unlike a normal steam flood, the steam is used as a heating agent to enhance the existing gravity drainage mechanisms, and project has proved to be viable based on encouraging pilot results. The elegance of the thermally assisted - GOGD is that the fracture network is both used for distribution of steam and recovery of the oil. The number of wells can therefore be kept to a minimum compared to conventional matrix steam floods. Whereas the primary production performance of the Qarn Alam under cold GOGD is only expected to recover 3-5 % of the oil in place, studies to date indicate that the recovery factor under steam injection at 18,000 tonne per day will be in the range 20-35 % with Oil Steam Ratio of 0.16 -0.3 m3 oil /tonne of steam. The learning from the Pilot has not only helped understand the subsurface uncertainties but also provided significant insight into the engineering design and operational issues which are being managed right upfront during design. Energy consumption in the full field development of this project is reduced by banking on the benefit from co-generation of power and steam. Utilisation of co-generation will minimise CO2 emission and reduce gas import. The project will be under construction from 2007, with full rate steam injection reached by late 2009. The paper not only discusses how the project addresses the reservoir management challenges of this complex recovery mechanism but will address some of the engineering and operational challenges that are being managed.
An Empirical Saturation Modeling of a Complex Carbonate Abu Dhabi Reservoir Using the Routine High-Pressure Mercury and Oil/Water Capillary Pressure Data
Authors: Basioni R. E. Mahmoud , Negahban R. E. C. Shahin , Dawoud Ahmed , El Mahdi Ahmed , Bahamaish T. L. Jamal
Published: December 2007

Minimizing uncertainty associated with predicted log water saturation can be best achieved through the integration of log analysis (formation evaluation) and capillarity (core measured high pressure mercury and oil/water drainage capillary pressure data). Further reduction of uncertainty in predicted formation water saturation requires; first the most probable log porosity solution interpretation; second the most probable log porosity/permeability relationship (match core measured values); and third a quantitative capillary pressure model that represents measured high pressure mercury and oil/water drainage capillary pressure data.

In this paper, the classical Leverett-J method (Leverett 1941) was used in the integration of capillary pressure data with routine core analysis and petrophysical rock types to generate a robust model for predicting formation water saturation profiles. The classical interpolation method that relates capillary pressure (derived from Leverett J function) to water saturation has been used predict the wetting phase saturation. The assignment of capillary pressure curves to their corresponding rock types was accomplished by grouping rock types according to discrete ranges of the interval speed which is defined as the square root of core measured permeability divided by porosity (k/φ) data. Each range of the interval speed will have a corresponding Leverett J function from which water saturations will be interpolated according to its respective height above the Free Water Level (FWL) (using the log predicted permeability-porosity ratios). In the absence of clear fluid contact, a trial and error method is used to adjust the FWL until a good agreement between the log predicted water saturation and the predicted water saturation from the capillary pressure correlation is reached. The error in averaging was minimized by increasing the number of rock types (minimizing the ranges of interval speed) using a large number of measured high pressure mercury and oil-water drainage capillary pressure data. Furthermore, this paper presents a comprehensive comparison of the log derived and model predicted water saturations.
Implication of Properly Tuned EOS and Properly Measured SCAL on Prediction of Rates, Reserves, and Field Performance Using a Full-Field, Fully Compositional Model for an Offshore Complex Carbonate Field in Abu Dhabi, UAE
Authors: Al Hajeri Salma , El Mahdi Ahmed , Negahban Shahin
Published: December 2007

Reservoir simulation is the most accurate tool for forecasting rates, reserves and field performance, provided that accurate information is used to build the model. To overcome major uncertainties associated with a fully compositional simulation model, it is of utmost important to obtain accurate SCAL data and EOS description. The accuracy of model initialization (including matches of log saturation profiles and oil in place) and prediction of historical field performance are strong function of these measurements.

This paper discusses the impact of newly measured SCAL data and a newly tuned EOS on model prediction for an off-shore complex carbonate field in Abu Dhabi, UAE. The subject reservoir has been put on production using a combination of Gas/Water/WAG injection schemes in early 2006. An advanced EOR/PVT study was carried out using representative oil and gas samples from the field. The results of experiments were used to build a new EOS fluid description. In addition, a detailed SCAL study was performed to measure pertinent relative permeability and capillary pressure data.

The interpreted SCAL data and the EOS description were tested extensively and then were used to update full field fully compositional model. The data was further verified during the history-match of the historical field data (early production scheme) before utilizing it for updating the forecast plan. Results indicated significantly improved reservoir performance prediction (increased ultimate recovery factor and production plateau duration) compared with the results of the previous model which uses non-accurate analog input data.

This paper will present implication of properly tuned EOS and properly measured SCAL on prediction of rates, reserves and field performance using a full field fully compositional model for an off-shore complex carbonate field in Abu Dhabi, UAE.
Tight Reservoirs—A Development Challenge Example From a Carbonate Reservoir Offshore Abu Dhabi, UAE
Authors: Al Hajeri Salma , Al Shehhi Abeer , Ribeiro Maria Teresa , Ayoub Mohamed , Negahban Shahin , Bahamaish Jamal
Published: December 2007

Tight carbonate reservoirs, although less well understood and believed to require higher development costs and risks than conventional reservoirs, have become an important resource. Historically, tight reservoirs have been unpopular and unfavorable with geologists and reservoir engineers mainly due to difficulty associated with their development with no commercial productive value. Recently, with the increase in demand for oil and continuous development of new technologies, the time is right to carefully examine and develop such reservoirs.

This paper discusses the development of one of the tightest carbonate reservoirs offshore Abu Dhabi, UAE. Initially, this reservoir was not planned to be developed based on the appraisal data collected. The average reservoir permeability is around 1 mD with a productivity index of 0.4 bod/psi. However, an intensive work was performed to evaluate the reservoir potential as being commercially attractive. Such process included gathering of additional data during the development of a major reservoir located below and the review of the core and test permeability data across the reservoir.

Several model scenarios were created both on static and dynamic sides as well as an evaluation of the uncertainties and associated development risks.

Effectiveness of the study took place when drilling horizontal wells across the most permeable intervals resulted in a production five times higher than expected. This resulted in a decision to embark on the field development and additional production data gathering for development optimization.
Improvement of Business Processes Through Knowledge Management
Authors: Gatta S. R.
Published: December 2007

Under the present budgeting system that is in vogue for many years, there is significant uncertainty concerning the Scope of Work (SCOW) at the Budget Proposal stage, giving rise to escalated cost estimates, which in turn lead to excessive carried over expenditure. That process gave rise to rush at the eleventh hour detrimental especially to the functioning of the executing arms (Controlling Groups) within the Company. A number of lacunae have been noticed. No feasibility study indicating the detailed evaluation of various alternatives and their economics was provided. The cost estimates are furnished without any front-end engineering. Sufficient time was not allowed to seek budgetary quotations. More often than not, nearly 50% cushion was provided in the estimated costs. Owing to these shortfalls inherent in the budgeting process, there was too much carried over expenditure with unspent funds (under-expenditure).

In an effort to resolve these shortcomings, the Company came forward with an innovative approach with the following merits:

▪ Precise cost estimates and implementation schedules, ▪ Precise capital expenditure phasing, thereby minimizing the Carry Over expenditure, ▪ Expedited project completion, incurring minimum or no project delays, ▪ Opportunity to apply value engineering to ensure quality at reasonable cost, ▪ More effective project appraisals, and, ▪ Well-defined Scope of Work, minimum number of variations to the original SCOW, minimum number of Authorization For Expenditure (AFE) revisions and minimum adjustment orders.

This novel scheme termed as Capital Project Proposals (CPP) Process was implemented within the corporate level Capital Investment Process through a management directive issued during Planning Group's Presentation in June 2002. The CPP Process provides the Company with a business practice that improves the development of the relevant capital project concepts and assists Top Management in their investment decision-making.

The case study presented through this paper adequately demonstrates the novel approach.
Enhanced Oil Recovery by Hot CO2 Flooding
Authors: Picha Mahesh Shrichand
Published: December 2007

Enhanced Oil Recovery (EOR) techniques helps to recover residue oil after Primary and secondary recovery of reservoir. This paper deals with a new Carbon Di Oxide (CO2) EOR technique, "HOT CO2" which includes combination of thermal and solvent techniques where miscibility and viscosity reduction are primary concern. In the proposed method CO2 will be superheated above the reservoir temperature to reduce the oil viscosities at the same time partially mix with crude oil which improves oil mobility. Heavy Oil field-Bati Raman from Turkey which is under CO2 Flooding, after the application of HOT CO2 flooding theoretical calculation shows it reduces the viscosity and partially mix with oil to increase the swelling factor which ultimately increase the recovery factor comparative with the CO2 flooding. Thus the screening criteria for HOT CO2 Flooding can now include highly viscous oil and covers wide variety of reservoirs which was not possible with CO2 flooding earlier. For the injection of HOT CO2 a special surface facility requires to prevent corrosive and thermal effect. Before implementation of HOT CO2 flooding method simulation model work, laboratory work and pilot field test are necessary areas to work. HOT CO2 flooding should be preferred absence of any major fault makes this technique more effective. "HOT CO2 flooding" will going to be one the best option for EOR in future.
A Novel Approach to Fracture Characterization Utilizing Borehole Seismic Data
Authors: Dutta Pradyumna , Singh Sunil Kumar , Al-Genai Jarrah , Akhtar Azhar , Akbar Mahmood
Published: December 2007

The Najmah, Sargelu and Marrat are the main Jurassic reservoirs in Kuwait. These fractured carbonate reservoirs with moderate to low porosity were deposited in an inner to mid ramp warm marine environment. The fracture systems play a significant role in production from these reservoirs and it is imperative to identify areas of high fracture density. It has been observed that fractures associated with certain faults have facilitated the flow in the Jurassic reservoirs. Identification of faults and associated fractures has been mainly based on 3D/2D seismic data, image logs, cores and thin sections.

A recent successful exploratory well in the Arifjan Prospect located on the eastern flank of the Greater Burgan Field, has opened up a large area which was previously considered to be nonproductive. There is excellent correlation between the fractures observed in cores, image logs and those predicted from the converted component of the zero-offset VSP. After registration of the z-component image with the converted image for various prominent reflectors, the discontinuities in the reflectors in the converted component image revealed fracture swarms which could be traced away from the well bore.

This technique of processing the VSP data to identify fracture clusters could form a bridge between surface and borehole data and improve confidence in predicting fracture swarms away from the well bore in addition to assisting in planning for future surface seismic and 3D VSP surveys.
Connection Qualification for Casing-Drilling Application
Authors: Lu Qing , Wu Jiang , Hannahs Dan
Published: December 2007

The advancement of casing drilling technology requires the casing connection to perform in more stringent conditions, i.e. in HTHP and directional wells under dynamic loading. Casing connection fatigue, sealing ability, and structural ability are therefore a primary concern.

As no commonly accepted industry standard exists in qualifying connections for casing drilling applications, a big question for the industry is how to qualify connections for casing drilling applications with a reasonable and practical approach. This paper presents the initial test results of connections for casing drilling applications with a new test procedure1, which combines the current industry standard ISO 13679 (the regular casing connection test specification2) worst-case tolerance strategy with dynamic loading testing (fatigue test simulating casing drilling condition3). The testing demonstrated the DWC/C-SR connection performance with the new test procedure. The predetermined service life was based on established fatigue SN curves4. The testing showed that the connection thread tolerance may greatly affect the connection fatigue life.

The performance characteristics of connections for casing drilling can be accurately defined by combining fatigue testing with ISO 13679 combined load testing. The initial test results presented in this paper will help illustrate connection performance characteristics and develop a test procedure for qualifying connections. This will result in improved casing drilling operation success and cost reductions.
Design of Well Barriers to Combat Circulation Losses
Authors: Aadnoy Bernt S. , Belayneh Mesfin , Arriado Miguel , Flateboe Roar
Published: December 2007

The paper summarize a 10 -year research program at the U. of Stavanger in borehole fracturing and mud design. Novel fracturing cells and mud cells were built to better understand the mechanisms that lead to circulation losses. Numerous experiments are conducted using both oil- and water based drilling fluids.

The paper presents a new mechanistic model for fracturing called "the elastoplastic barrier model". It is different than other recent models, and it is verified with lab experiments. In simple terms it defines optimal barrier filtrate loss to place particles in the loss zone, and, also the mechanical strength of the particles required to resist losses. Selected lab experiments will be presented demonstrating that borehole fracturing resistance can be significantly improved by changing the mud composition.

Testing commercial LCM products it was found that some worked well, some were poor, and some worked only in synergy with others. Based on this, the compostion of an optimal LCM pill will be presented. Non-petroleum products have also been tested to search for improvements in mud design. One result is that calcium-carbonate can be replaced with more efficient materials. We have also shown that adding small amounts of carbon fibre have a positive effect.

This research has been conducted in close cooperation with major mud companies and operators. A field case will be presented from a shallow field. The mud was designed and tested during operation at the lab of the U.of Stavanger. The result was a clear increase in fracture pressure, resulting in a successful operation.
State of the Art in Geophysics and Wells Imaging for Giving a New Lease of Life to Giant Brownfield
Authors: Sanchez-Perez Zayda , Baud Emmanuelle , Jeanjean Frederic , Cassou Gilles , Lesueur Jean-Louis
Published: December 2007

The Abu Al Bukhoosh field extends offshore Abu Dhabi, near the UAE-Iran border. More than thirty years of production from the Upper and Lower Arab, but also Thamama reservoirs, under secondary and tertiary development schemes, allowed reaching significant recovery factor. At this time in the life of this very mature field, further applications of EOR techniques for enhancing the final field recovery lead to a deep revamping of the geological models.

The reprocessing of the 3D seismic data in 2002-2003 strongly improved the resolution and continuity of the reflectors. Despite evidenced through dynamic data, the second-order structural framework of this finely layered shallow-carbonate environment remains unclear.

The use of new filtering, and seismic-derived attributes combination significantly improves the structural interpretation. Noise attenuation, vertical discontinuities and horizon continuity enhancement provide a better imaging for faults and sub-seismic faults.

Among the newest attributes available in SISMAGE™ TOTAL proprietary software, the fault attribute associated with the "fault peeling" techniques were of crucial help for highlighting small-scale structural features.

It appears that most of the main faults were vertically and horizontally segmented and should not be treated in a reservoir model as linear vertical or slightly deviated straight line. In addition, several relays on these main faults have been defined, the most important ones being located at the intersection with broad diffuse N020-030 oriented trends.

The location of these trends and their relation with the second-order N110-120 oriented structural features should provide key for understanding the dynamic governing the flow regimes of the field.

Finally, a fully integrated approach from Geophysics and Geology to Reservoir leads to review the structural heterogeneity of the field. This achievement was a prerequisite for building representative simulation models mandatory to pursue IOR/EOR developments.
Kick Detection and Control in Oil-Based Mud: Real Well-Test Results Using Microflux Control Equipment
Authors: Santos Helio , Catak Erdem , Kinder Joe , Sonnemann Paul
Published: December 2007

Kick detection in oil and synthetic-based fluids has been a major concern for the industry for decades. Due to solubility issues, kick detection may be delayed and resulting well control operations may be problematic. Use of the Micro-Flux Control (MFC) method potentially offers a better way to address this problem in the same way it has been successfully demonstrated to work using water-based fluids (WBM).

To check the performance of the MFC method while using oil-based mud (OBM), a series of full-scale tests were conducted at Louisiana State University PERTT Laboratory using natural gas injected into test wells containing an 11-ppg 70/30 diesel/water OBM. Performance results were compared with results previously obtained with WBM gathered at the same facility.

The excellent and consistent character of the test results obtained encouraged the use of the MFC on a well to be drilled in Texas for Chevron. The well plan called for using OBM with mud density up to 17.4 ppg, at an anticipated depth of 13,000-ft. This would be the second well drilled with the MFC method, following one drilled in Brazil for Petrobras using WBM.

The paper presents the results obtained during the one – week long live well testing at LSU as well as details of the first field test of the MFC system on the actual well drilled with OBM in Texas. The results confirmed the ability of the MFC system to detect very small influxes of natural gas into OBM with subsequent control of the influx accomplished in a way very similar to that used with WBM. Several other tests were also performed in both wells to explore possible additional uses of the MFC system. These included dynamic leak-off and formation integrity tests, behavior with multiple kicks inside the wellbore simultaneously, identification of ballooning or "breathing" during connections, and early detection of loss of circulation. All of the results obtained in both test scenarios confirmed the potential value of the MFC system for identifying and dealing with the above listed issues when conducting drilling operations utilizing OBM.
Rotary Steerable System Technology Case Studies in a High-Volume, Low-Cost Environment
Authors: Akinniranye G. , Kruse W. D. , Bautista Gomez A. , Poedjono B. , Dubose B. , Goobie R. B. , Hobin J.
Published: December 2007

An efficient, safety-conscious wellbore drilling method features highly accurate wellbore placement, reduced drilling time, and improved safe drilling practices. Rotary steerable system (RSS) technology provided a cost-efficient solution in a high-volume environment for a US-based oil and gas exploration company drilling 80 to 100 wells per year in South Texas, USA.

Although vertical drilling has been in practice since the birth of the industry, maintaining verticality is still challenging and requires alternative drilling strategies. Traditionally, downhole positive displacement motors (PDMs) have been used to control the wellbore vertically in this drilling environment. This drive system typically requires one or two additional bit runs to achieve the target objectives. A reduction of the weight on bit (WOB), or feathering, was also required to maintain a vertical wellbore. The combination of this drive system coupled with the lower-than-optimum WOB leads to a dramatic reduction in rate of penetration (ROP) when steering is required, which is neither cost-efficient nor desirable. The introduction of RSS technology has addressed both of these concerns by allowing the application of higher WOBs for faster ROP while maintaining high levels of wellbore placement accuracy.

RSS technology in this environment increased the number of drillsites available as the surface location can be right on the "hard-line" of 467 ft from the lease-line required by the Texas Railroad Commission. Previously, fewer lease-line wells were drilled owing to the problems of keeping the accumulated displacement inside the lease dimensions.

This paper presents field studies from 2004 to 2006 demonstrating RSS success in maintaining verticality where the bit tends to walk related to highly faulted, fractured, and dipping formations. The RSS system provided real-time response and a vertical wellbore. Instantaneous wellbore corrections reduced drilling time in some cases more than 40%. In both the vertical and deviated wellbores studied, total depth (TD) was reached ahead of schedule with reduced costs.
The Introduction of Electromagnetic LWD Technology in Saudi Arabia—A Case History and Future Application to Underbalanced Campaigns
Authors: Muqeem M. A. , Jarrett C. M. , Jeffri A. M. , Weisbeck D. , Mallahy M. , Forge N. , Branch A. J.
Published: December 2007

The first Electromagnetic-Logging While Drilling (EM-LWD) Triple Combo operation with the Extended Range set-up was successfully completed in Saudi Arabia. The 6-1/8 inch horizontal section of the well was underbalanced drilled (UBD) from 8,109 feet to 11,189 feet in one run.

The objective was to evaluate the feasibility of EM transmission in conjunction with LWD triple combo and annulus pressure sensors in the 6-1/8 inch horizontal section. LWD is necessary for geo-steering of the well, and annulus pressure is required to monitor the underbalanced conditions. This particular well was drilled UBD with single phase fluid; future wells will require the use of gas injection to achieve UBD conditions. The injection of gas through the drill pipe precludes the use of mud pulse telemetry. As an alternative, EM telemetry needed to be proven to allow a continuation in the UBD planning process to include real-time LWD technology.

EM transmission of LWD triple combo and annulus pressure data in real time allowed 3,080 feet of 6-1/8 inch horizontal section to be successfully geo-steered and drilled in one bit run while maintaining underbalanced conditions. In addition, the well was flow and pressure tested with real time annulus pressure data acquired during pumps off operations (an advantage of EM versus conventional mud pulse telemetry is that real-time updates are possible, independent of well bore hydraulics). The conclusion was the successful EM-LWD operation in the well where all of the objectives were achieved.

The successful proof-of-concept of EM-LWD with annulus pressure extends the scope of development of future UBD campaigns that require two phase fluid utilising drill pipe gas injection.
Field Result of Equivalent-Circulating-Density Reduction With a Low-Rheology Fluid
Authors: Bolivar N. , Young J. , Dear S. , Massam J. , Reid T.
Published: December 2007

To qualify for use on a world record extended reach drilling (ERD) well, a trial well was selected to demonstrate the technical benefits of using a uniquely designed, low-rheology, synthetic-based drilling fluid. The 8½-in., production hole section was 1,755 ft (535 m) long and drilled to 20,472 ft (6,240 m) at an angle of 25°. Prior to drilling this section, a low-rheology drilling fluid was selected. Selection analysis was based on assessment of key drilling parameters as compared with wells drilled previously using a conventional API barite-weighted synthetic fluid. A unique characteristic of the low-rheology drilling fluid is its use of specially treated, micron-sized, barite-weight material (TMSB). It can be formulated with a much-reduced rheological profile without the risk of barite sag.

This paper presents the background work performed leading up to the field trial. Field data is presented comparing the drilling performance and fluid characteristics between the low-rheology fluid and the previously used conventional API barite-weighted synthetic fluid system. Significant reductions in equivalent circulating density and standpipe pressures were accomplished, as well as torque reductions of up to 30%. Results demonstrated the low-rheology, synthetic-based drilling fluid's ability to reduce drilling risk. This paper reports the economic and technical benefits realized from using this fluid, including the first use of 400-mesh prototype shaker screens (API 200 mesh), the much reduced dilution factors, and cuttings re-injection volumes.
Managed-Pressure Drilling Reduces China Hard-Rock Drilling by Half
Authors: Shen Chen , Niu Xinming , Nas Steve , Holt Calvin
Published: December 2007

This paper describes the experiences of nine months of managed pressure drilling (MPD) operations conducted in hard-rock and sour-gas formations in the Sichuan Province of southwestern China. Percussion drilling with compressed air and foam was applied in both top-hole and nuisance-gas formations, while near-balanced operations are being planned for the sour-gas reservoir.

Initially a two-well project, it was commissioned to determine whether percussion air drilling technology could provide rate-of-penetration (ROP) benefits. Because the feasibility report determined that wellbore stability could be an issue, a certain amount of project risk was involved. In addition, the main reservoir is sour, and potential sweet-gas secondary zones are located above it. Conventional 5,500-m wells were being drilled and completed in +350 days. The first air-drilled well was spudded in March 2006, and immediate benefits were realized. More than 60 days in the main 311-mm section were saved. Subsequent wells (+4) have improved ROPs by 94%, eliminating an additional 60 days from the drilling curve. Wells are currently being drilled in 240 days.

As the project progresses, near-balanced drilling, using MPD techniques, will be applied in a stepped approach to drill the sour-gas reservoir, improve ROP performance, and reduce overall well times.

Weatherford is the only western service company in the field, and lessons learned during this project have significantly affected MPD and percussion air drilling in China. Enhanced engineering reviews, better implementation of procedures, management of change processes, improved client awareness, and closer co-operation between service provider and operator are enabling successful execution of remote MPD projects in China and Asia Pacific.
Unique Pivot Stabilizer Geometry Advances Directional Efficiency and Borehole Quality With a Specific Rotary-Steerable System
Authors: Barton Steve , Clarke Alan , Perez Daniel G. , Peach Simon
Published: December 2007

The geometry of a stabilizer, when it is used as a near-bit pivot within specific point-the-bit rotary-steerable bottomhole assemblies (BHAs), is critical to both stability and deflection to provide optimal directional response. This paper describes the testing of a rotary-steerable system (RSS) and unique ring gauge pivot stabilizer at a purpose-built, full-size drilling test facility. The extensive, systematic testing of a point-the-bit RSS with both full ring gauge and conventional pivot stabilizer has enabled a direct comparison of the directional response, hole quality, and drillstring vibration to be made for the various combinations tested.

Aside from comparison of the ring gauge stabilizer against conventional pivot, the testing also evaluated the interaction between the gauge design of the bit and the pivot stabilizer. Test monitoring required use of a proprietary downhole dynamic data recorder (DDDR) in a specially modified housing. The DDDR was used to assess both lateral and torsional stability of the stabilizer geometries and their relationship with bit gauge style and length.

Further to the laboratory testing, trial applications have been sought where severe vibration issues are problematic to efficient operation of the RSS. Use of full ring stabilization geometry with an RSS in these applications will advance the industry's understanding of downhole dynamics. Enhanced understanding, in turn, will enable more efficient drilling of better-quality directional wellbores, significantly reducing cost per foot.
Development of a Deep-Penetrating Emulsified Acid and Its Application in a Carbonate Reservoir
Authors: Sarma Dilip Kumar , Aggarwal Pavan , Rao Eashwar , Kumar Pradip
Published: December 2007

The goal of matrix stimulation of carbonate reservoirs is to improve near wellbore conductivity by generating wormholes and increasing the effective wellbore radius, bypassing damaged areas. In naturally fractured carbonates, the wormholes connect the existing fractures, creates longer flow channels. Most widely used stimulation method in carbonate reservoirs is matrix acidization using HCl with various concentrations. The rapid reaction of HCl with carbonate matrix does not allow the reactive fluid to penetrate deep inside the formation before the acid spends. Therefore, the efficiency of conventional acid is limited, where deep penetration is needed. Stable emulsified acids are found very effective, to combat the challenge. The basic advantages of using emulsified acid are: generates longer wormholes by deep penetration into the formation; better zonal coverage; preferential stimulation of oil zones and less corrosive to workstring and downhole/surface equipment.

Based on the extensive laboratory studies, a stable deep-penetrating emulsified acid has been developed for carbonate reservoirs. The formulation is a mixture of HCl with compatible additives, diesel and some suitable emulsifiers. The ratio of the dispersed acid and external diesel phase is maintained as 70:30. Stability of the system is a major concern for adequate retardation and penetration deep inside the reservoir. Stability of emulsion largely depends on reservoir temperature and the HLB number of emulsifier. Two surfactants were identified for the system and the HLB number has been maintained in the range of 5.1-5.2 by optimizing the ratio of two surfactants for achieving the maximum stability. The developed acid system has been applied in some wells of an offshore field of India with encouraging results. The field comprises of naturally fractured limestone formation with number of hydrocarbon bearing sands. This paper describes the development of the Deep Penetrating Emulsified Acid and its application in the field along with treatment methodology and outcomes.