bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Fracture Face and Formation Plugging in Injection Well Fracturing and Injectivity Decline
Authors: Saripalli K. Prasad , Bryant Steven L. , Sharma Mukul M.
Published: December 2007

Particle plugging of wells in the near wellbore region can have an important influence on the initiation and propagation of thermally and hydraulically induced fractures during water injection. Fracturing in turn can significantly influence the rate of injectivity decline in water injection wells. Development of models that elucidate the role of plugging of the fracture face and surrounding formation on the growth of fractures, and the resulting injectivity behavior, is an important research need. We present a model to predict the initiation and growth of a fracture in the near wellbore region due to the combined influence of injection pressure, changes in pore pressure, thermal stresses due to the injection of cold water, and an additional pressure drop due to particulate plugging. Fracture growth and fracture face plugging are modeled as dynamically coupled phenomena. The results indicate that wellbore plugging can significantly affect the initiation of a fracture. Further, plugging of the fracture face itself can have a major impact on the growth of the fracture, and the overall injectivity of the well. It is found that at a given injection rate, an increase in plugging leads to significant increases in fracture half-length. Results also demonstrate that a longer fracture does not necessarily imply an increase in injectivity, if there is significant permeability impairment due to plugging of the fracture face. The effectiveness of fracturing as a well-stimulation mechanism can be seriously diminished due to fracture face plugging in injection wells.
Shallow Water Flow Planning and Operations: Titan #1 Exploration Well, Deepwater Gulf of Mexico
Authors: Schuberth Paul C. , Walker Mike W.
Published: December 2007

Shallow water flows (SWF) from overpressured aquifers have been a persistent problem in the deepwater Gulf of Mexico (GOM) and can create significant financial and operational risks for exploration and development drilling programs. For the GOM, shallow water flow intervals typically occur between 300 ft to 2500 ft below mudline (BML) and in water depths greater than 1500 ft. If left unchecked, the disturbance from the water flow can cause loss of soil strength surrounding the wellbore, thereby compromising the structural integrity of the well. In industry, extreme cases have led to collapsed casing and/or total loss of wellbores.

The Titan No. 1 exploration well was drilled in Garden Banks Block 785 (GOM), in 4640 ft of water. At Titan, the planning and successful implementation of operational procedures designed to mitigate the risks associated with SWF hazards included: performing a shallow hazards assessment, preparing and implementing SWF contingency plans, identifying the SWF zone quickly, immediately controlling the water flow zone with weighted mud (while drilling riserless), and using nitrified foam cement to seal off the water flow behind 20" conductor pipe. Operations at Titan were based on the philosophy of quickly identifying the SWF, and immediately stopping the flow with weighted mud, as the chance of successfully mitigating the flow and maintaining the structural integrity of the wellbore will likely decrease with time if the sand is allowed to produce water, sand and/or sediment.
Problems of Ultra-Deepwater Drilling
Authors: Shaughnessy J. M. , Armagost W. K. , Herrmann R. P. , Cleaver M. A.
Published: December 2007

Ultra-deepwater drilling activity is at an all time high. Recently, there were only two rigs rated to, and actually working in, water depths greater than 6,000 ft. Soon there will be over twenty. This increase will involve new deepwater operators and bring a large number of new people to deepwater. This paper presents some of the problems that have occurred in deepwater operations under the assumption that an understanding of what can go wrong is the best way to avoid problems. It will identify these problems and discuss the critical topics of rig positioning, environmental considerations, BOP control, riser management, well control, wellbore construction, production problems, and personnel training and safety.
Drilling Performance Guidelines - A Tool for Sharing Drilling-Related Knowledge and Experience
Authors: Curry D. A. , Singelstad A. V. , Bowden D.
Published: December 2007

A major operator and a service company have collaborated to produce an on-line knowledge base, with the objective of helping their personnel achieve consistent good drilling performance.

The knowledge base is a highly structured electronic manual which provides a tool for drilling engineers to use in day-to-day operational work, a training aid for new engineers, and a one-stop reference source for drilling engineers, geologists and petroleum technology workers. It is a "living document", updated to reflect advances in technology and understanding.

This paper describes the knowledge base content, structure and mode of use, demonstrates its advantages over a conventional paper manual, and shows it to be a powerful tool for capturing and sharing drilling performance-related knowledge and experience.
Compression of Downhole Data
Authors: Bernasconi G. , Rampa V. , Abramo F. , Bertelli L.
Published: December 2007

Measurement-While-Drilling (MWD) services efficiently support drilling decisions, therefore these tools are becoming a de-facto standard on well sites. Currently, the main drawback of MWD equipment is the absence of a high bit-rate telemetry system to enable real-time activities. This problem may be solved by employing either an off-line solution, with limited memory capacity up to few hundreds of Mbytes; or an on-line solution with telemetry at a very low bit-rate (tens of bits/sec). However, following the off-line approach with standard acquisition parameters, the internal storage memory would be filled up in just a few hours at high acquisition rates. On the contrary, with the on-line solution only a small portion of the acquired signals (or only alarm information about potentially dangerous events) can be transmitted in real-time to the surface by using mud-pulse telemetry. In this paper, we present a lossy data compression algorithm based on the wavelet transform (WT), which is suitable for downhole implementation and may be successfully applied to both on-line and off-line solutions. Numerical tests based on real field data achieve compression ratios up to 15:1 without noticeable signal degradation. This allows a significant increase in downhole time acquisition and in real-time information that can be transmitted through mud-pulse telemetry.
Drilling and Completion of Horizontal Wells Requiring Sand Control
Authors: Burton Bob , Hodge Richard
Published: December 2007

Horizontal wells are often used to increase production rates and improve recovery. The increased inflow area and ability to penetrate/drain multiple targets make horizontal wells a cost-effective producing strategy in many oil and gas developments. However, analysis of horizontal wells requiring sand control indicates that many wells completed with sand control screens suffer from poor inflow performance. Previous studies have shown that screen plugging by residual Drill-in Fluid filtercake can lead to severe flow impairment. To minimize the potential for screen plugging, various drilling and completion practices have been tried with varying success.

This paper discusses well damage mechanisms, investigating the impact of the magnitude of different types of damage on well inflow performance. Critical damage mechanisms are highlighted and methods of preventing or remediating damage are discussed. The results of laboratory testing of Drill-in Fluids and cleanup/remedial treatments are compared to field case histories to illustrate the importance of Drill-in Fluid maintenance, treating fluid composition, and treating fluid placement.
Consequences and Relevance of Drillstring Vibration on Wellbore Stability
Authors: Santos Helio , Plácido J. C. R. , Wolter Claudio
Published: December 2007

Historically, wellbore instability problems have been mainly attributed to the physico-chemical interaction between the rock and the drilling fluid, especially when this is a water-based fluid (WBM). However, recent studies have shown that these chemical effects may be irrelevant in comparison with other energetic events which are present during the drilling operation of a well. Excessive drillstring vibration has been identified as such an event that can cause a great amount of damage to the wellbore. Although some studies present clear indications that the reduction of drillstring vibration has led, in many occasions, to an improvement on instability problems, still today this item only deserves attention from equipment divisions, aiming at reducing drillstring fatigue problems.

The main objective of this paper is to show the clear existing relation between excessive drillstring vibrations and serious well instability problems. It is shown, in energetic terms, that drillstring vibration, when having enough lateral amplitude to hit the wall, is responsible for irreparable damage to the borehole. Simple ways of quantifying vibration effects in terms of energy are presented. The paper also presents field measurement data, obtained with surface vibration sensors, which clearly allow identification and correlation between vibration problems and wellbore instability, through the comparison of these vibration records with caliper logs.
Underbalanced Drilling Gains Acceptance in Europe and the International Arena
Authors: Gedge Ben
Published: December 2007

Underbalanced Drilling is the natural and inevitable technological progression of horizontal drilling developed in the United States Austin Chalk formation, primarily for field re-development and now extended to new reservoirs where impairment is a key issue.

Horizontal drilling greatly improved recovery and productivity rates, particularly in redevelopment of existing and often pressure depleted reservoirs, but still encountered many of the drilling problems associated with conventional directionally drilled wells. In the case of mud losses, impairment and formation damage, the problems increased due to the wellbore being open for much longer and of course having much greater length through the reservoir section. Operators around the world quickly saw the advantages of horizontal drilling, which rapidly became a standard field development technique, onshore and offshore where the geology and reservoir were compatible with this method of development. The same now applies to underbalanced drilling. The advantages are quickly being seen and the technology employed where the geology and reservoir are suitable.

The majority of hydrocarbons being exploited today are found in existing fields or in complex and lower quality reservoirs. This is where underbalanced drilling technology can improve recovery and in some cases reduce development costs.
High Strength Sour Service C110 Casing
Authors: Urband-P.E Bruce E. , Morey Steve
Published: December 2007

Drilling high pressure, high temperature (HP-HT) wells over the last several years has brought forth and accentuated the need for higher strength OCTG (Oil Country Tubular Goods) grades which are suitable for use in sour gas environments.1, 2 Drilling engineers are designing casing strings at depths where higher strength is needed. The presence of hydrogen sulfide has traditionally restricted the use of casing grades with minimum yield strengths from 90 to 95 KSI (API Grades C90 and T95). Recent advances in metallurgy and pipe making now enable the drilling engineer to utilize high strength, sour service (HSSS) tubular grades with minimum yield strengths from 100-110 KSI (C100, C105 and C110).

This paper discusses the metallurgical attributes of high strength, sour service (HSSS), tubular goods and provides information about specific cases where without HSSS grades successful, economic completions would not be possible. The paper also discusses the manufacturing techniques and material properties necessary to assure that casing products are suitable for use in sour environments at high pressures. A brief history and description of many of the API casing and tubing grades are discussed relative to their properties and intent for sour service applications. Details of the testing necessary to assure proper serviceability when exposed to hydrogen sulfide (H2S) are provided. Specialized testing, which the National Association of Corrosion Engineers (NACE) has standardized for oil and gas production equipment will also be discussed. Information is provided on both casing and coupling stock with thickness’ that have been traditionally difficult to assure the metallurgical uniformity and resistance to hydrogen sulfide stress cracking (SSC).
Application of Dope-free Tubular Connection to SAGD and its Works
Authors: Tsuru Eiji , Tsukano Yasushi , Wakishima Ryohei
Published: December 2007

This study deals with the laboratory test results on the application of a dope-free connection (DFC) to a steam injection well, and the running results in the actual well.

A mechanical shock test, thermal shock test, and make-and-break (M&B) test were performed to evaluate the durability and the galling resistance of DFC with the new surface treatment. In addition, the effect of coating damage on the connection performance has been investigated. Under the predicted loading conditions, the connection performance was evaluated. The connections were used in steam assisted gravity drains (SAGD).

As the results of the test, it was found that DFC have enough galling resistance at an extremely low temperature and after a thermal shock was applied thereto. The galling resistance was not degraded in the case of a connection having a solid lubricant with coating damage. The joint strength and the gas tightness were maintained under repeated tensile and compressive loads at an elevated temperature. In the field usage, all connections were made-up without any thread compound grease (TCG), so that their running efficiency could be improved.

In conclusion, it is apparent from the results of the tests that DFC can endure field application. DFC not only eliminates the environmental problems caused by TCG, but also has some potential for saving running time.
Dieksand 2; an Extended Well Through Salt, Increases Production from an Environmentally Protected Field
Authors: Sudron Ken , Berners Heinz , Frank Ulrich , Sickinger Werner , Hadow Anthony , Klop Govert
Published: December 2007

The Mittelplate Field is being developed from the North Sea's only drilling artificial island and is Germany's largest producer. However, the tidal flats around the island became an environmentally protected nature reserve, which limited significant increases in production. This changed with the onset of extended reach drilling techniques, where drilling from shore proved to be a feasible option. The consortium of RWE-DEA AG (operator) and Wintershall AG, established an International Drilling Team and concentrated its engineering effort on the ERD well, but in particular the contingencies for the well due to the need to intersect a salt dome at high inclination and the limited amount of available geological information. It was these contingencies that influenced changes to a conventional ERD approach, by increasing top-hole sizes and casing specifications. This then had a knock-on affect to other techniques, such as achieving directional control and ensuring sufficient hole cleaning, whilst being hampered by known well-bore stability issues, such as the effects of salt tectonics. Known risks were reduced by upgrading the rig capabilities, incorporating an ERD customised profile, utilising friction reducing techniques, casing centralisation and cementing procedures. The well was finished in 159 days and reached 7727 m MD (TVD 2019 m), with a horizontal displacement of 6938m.

This paper outlines a case study of the well, through planning, execution and evaluation, that sets guidelines to engineer further ERD enhancements as the risks are reduced.
Borehole Stability Assessment Using Quantitative Risk Analysis
Authors: Ottesen S. , Zheng R. H. , McCann R. C.
Published: December 2007

A new wellbore stability analysis method based on Quantitative Risk Analysis (QRA) principles is described in this paper. Limit state functions that define the limit for failure (stuck pipe due to excessive breakout) and success (operationally tolerable magnitudes of breakout) are defined as functions of wellbore trajectory and geometry. Stochastic input data for the QRA procedure, which incorporate uncertainties in model input parameters, are generated by a fully three-dimensional wellbore stability model. Modeling results yield probability of success as a function of drilling fluid density. A field application of the method is presented to illustrate the viability of the analysis.
Hardbanding And Its Role in Deepwater Drilling
Authors: Mobley John G.
Published: December 2007

Hardbanding of drill pipe tool joints and other drilling equipment has been around since the late 1930's. Originally, hardbanding was applied primarily to protect the drill pipe and other tools from premature abrasive wear. Since that time, there have numerous changes in hardbanding and its application, but only within the last few years has new technology been introduced that allows hardbanding to protect the casing, the marine riser and the drill pipe at the same time.

Hardbanding is one of the most simple yet most misunderstood products being used on a drilling rig today. Along with the new technology being utilized to drill the highly deviated wells such as horizontal, ERD, or multi-directional, comes the problem of creating excessive downhole drag and torque. All of this drag and torque creates friction, which, in turn, creates wear on the drill string, the marine riser and the casing. Today, there are several types of wear resistant alloy hardbandings on the market. Most of them are designed to protect either the casing, riser or the drill string, but only one or two of them can sufficiently protect all of them at the same time.

Though the wear resistant alloy hardbanding technology has only been on the market for 6-8 years, it has gained increased popularity over conventional tungsten carbide hardbanding for several reasons. This technical paper will attempt to address these points in order to educate concerned parties as to which hardbanding to use in a particular situation.

The proper hardbanding with the right application can: Substantially increase the tool joint wear lifeGreatly reduce casing wear caused by the drill stringSubstantially reduce downhole drag and torqueReduce rig fuel consumptionAllow operators to run lighter weight and grade casing
Risk, Exploration and Hydrocarbon Property Evaluation: Comparison of Alternative Theories
Authors: Stauffer Thomas. R.
Published: December 2007

A method is presented for fully risking projects such as exploration ventures or the acquisition of undeveloped reserves. The expected value will in general overstate "value" because it does not reflect the uncertainty in the project, as measured by its variance or standard deviation. If the expected value is calculable, then the risk- adjusted value ("RAV") can also be calculated. The RAV depends additionally upon the size of the exploration budget compared with the project and also upon the "price of risk". That price is incorporated from the finance literature. The technique permits answering three related questions: 1) the risk-adjusted rate of return for a given project; 2) the risk-adjusted value of that project; or 3) the risk premium appropriate for a particular project given the size of the firm's exploration budget.
Conversion of Air Permeability to Liquid Permeabilities Extracts Huge Source of Information for Reservoir Studies
Authors: Macary Sameh M.
Published: December 2007

Permeability data form great part of data input in all of simulation studies. The importance of permeability data increases as the production life of oil fields becomes to later stages. However, the industry has a huge source of only air permeability measurements and a little number of liquid permeability values due to the relatively high cost of special core analysis. The present study suggests a correlation to convert air permeability into oil and brine permeabilities for Nubia "C" reservoir. Data of more than one hundred samples were gathered from 16 wells that are producing fore fields: October, Ramadan, East Tanka and Sidki. The data of other three fields: Hilal, Gebel El-Ziet, and Ras-Budran were used for to confirm the validity of the derived equations for oil and brine permeabilities. The comparison with the commonly used tables of Amoco conversion shows a higher accuracy and more consistent results over a wide range of permeability values. The conversion of air permeability to liquid permeabilities forms a cost-effective method for coring. The new correlation also introduces more feasible estimation in case of loose and poorly consolidated sands, or in case of the unavailability or invalidity of old cores to carry out oil and brine permeabilities. Further, the conversion formula offers the possibility to make a better use of the large amount of old air permeability data obtained through routine core analysis for the various further uses in geological modeling, reservoir simulation studies, reservoir surveillance/monitoring and production technological work.
Application of Geostatistical Modeling in an Integrated Reservoir Simulation Study of the Lower Bahariya Reservoir, Egypt
Authors: Aly Ahmed , Lee W. John , Datta-Gupta Akhil , Mowafi Khaled , Prida Manuel , Latif Mahmoud
Published: December 2007

This paper presents the application of geostatistical modeling to capture the reservoir heterogeneity in a Lower Bahariya reservoir, Western Desert, Egypt. "Conventional" geologic modeling in the highly heterogeneous Hayat Yasser field was not adequate to capture the heterogeneity and address the objectives of our study of the field. Previous studies were not successful in modeling this field due to the high level of heterogeneity. We used geostatistics to integrate well log, geologic, and core data to develop a 3D model that honors well data exactly and imposes spatial continuity relations derived from variography. Our modeling approach consisted of generating a three-dimensional porosity distribution using ordinary kriging and generating permeability realizations using a "cloud transform" that uses the porosity distribution in conjunction with the porosity/permeability scatter plot based on core data. The cloud transform technique uses concepts from conditional probability to preserve the inherent scatter in the porosity/permeability relationship.

In this paper we will present the geostatistical model selection, model validation (dynamic history matching) and model forecasting. We also present new techniques for quickly identifying the most promising areas for redevelopment in the reservoir prior to optimizing reservoir management strategies with the simulator.

Our conclusions and recommendations, based on the results of this study, will help improve future management and development of similar waterfloods in the region.
Enhancing Low Productivity Wells Using Special Gas Lift Design
Authors: Fotouh Mahmoud Aboul , Eissa Moh. , Al Gharabawy A.
Published: December 2007

Artificial lift using gas is considered the main source of life for most of Gupco's wells. Since employing gas lift technology in 1972, Gupco managed to improve total oil recovery and increase daily production rate in its operations. The conventional procedure for lifting well fluids by injecting compressed gas through gas lift valves using continuous gas flow design has realized significant production benefits over the years. But now due to the changing reservoir conditions, primarily declining reservoir pressure, an innovative approach to gas lift technology must be utilized to conserve available lift gas volumes while avoiding ineffective circulation of gas through the deep operating gas lift valves. Gupco overcame this problem by designing and implementing a system, which uses a combination design of continuous and intermittent gas lift procedures. The results of using these designs are very good, keeping wells on production when often time would be shut-in due to limitations in gas lift capacity. the gain is not only realized from maintaining wells on production, but also through redistribution of the additional volumes of high pressure gas. One of many success stories in Gupco is the case history of Morgan well M-41 where 1000 BOPD gain was realized while saving 1.5 MMSCFD of high pressure gas through the use of fluid operated and Pilo-Port valves rather than continuous injection. This new design is not common in operation around the world, but Gupco has effectively used this technique in improving production performance and is considered an industry leader. This paper will demonstrate all aspects of designing an installation, the advantages and disadvantages of this approach, and the detailed results of Gupco's success story. For this reason, we can now say that no gas is being wasted and we are getting maximum benefit from our gas lift investment.
A Challenge to Meet Environmental Law Number-4, A Comparative Evaluation Between Water-Treating Modified Systems and Other Available Oil - Water Separation Techniques
Authors: Kenawy F. A. , Kandil M. E.
Published: December 2007

Recent regulations, as per Environmental Law No. 4, prohibit disposing industrial wastes without necessary treatment to remove impurities and pollutants. In general, oily waste water treating equipment are categorized as 1) primary treatment equipment to protect the downstream facilities from surges and upset conditions, 2) secondary treatment equipment for bulk oil removal, or 3) tertiary treatment equipment to remove very fine oil particles. However, economics, size of equipment and simplicity of operation favored only the traditional oil-water separation facility to do the essential primary treatment. Therefore, in order to meet new environmental regulations while using only traditional oil-water separation facilities, it is necessary to improve its effectiveness for oil-water separation. A comparative evaluation study had been done to determine the feasibility of developing the currently used traditional systems including ballast ponds, API separator, CFP separator, outfall line, slop oil tanks, probes and possible waste-water re-injection.
Innovative Solutions in Developing Marginal Gas Fields East Shukeir Marine (ESMA) Gas Field
Authors: Shaheen Emam M. , Schultz Steve
Published: December 2007

The East Shukeir Marine (ESMA) gas field is located on the east side of the north bound shipping lane of the Gulf of Suez. It was part of the British Petroleum Company concession in 1985 when the ESMA-2 well was drilled, the analysis of open hole logs and DSTs concluded a limited reservoir and non-commercial reserves from the Kareem sandstone. Therefore, it was abandoned in July, 1985. In May, 1993 the concession was awarded to AMOCO.

The objective of this paper is "Demonstrating the ESMA reservoir development alternatives including various production schemes to achieve the highest shareholder value". Development plans included implementation of multidiscipline geological / engineering evaluations to justify reentry, acquisition of additional tests, test results analysis, reserve estimation and selecting the most economically attractive development scheme to bring the reservoir on production.

The critical question was "What is the size of the reservoir"?. Old DSTs indicated small area (45 acres), but without boundary effects. GUPCO's assessment using 3D seismic and pressure data reflected a larger area and inconclusive DST results. Re-entering the well to run an extended pressure test appeared to be the best technical solution. A risk analysis approach was used to conservatively bracket the potential ranges of drainage area. Results indicated a probability of economic success for reentry.

Extended DSTs for both oil and gas columns were performed after reentry. Results indicated a larger reservoir size (300+ acre area) and higher reserves (26 BCF and 1.5 MMBO) with production rates of 20 MMCFPD and 2000 BOPD.

Subsea technology was utilized to economically justify development of this one well marginal field. Application of a low cost subsea tree and 4.5" coiled tubing production line was utilized to capture the reserves. In November 1997, GUPCO put the well in production at 10 MMCFD and 2000 BCPD.
Prediction and Evaluation of the Impact of Reservoir Souring in North Kuwait, A Case Study
Authors: Al-Rasheedi Shamaa , Kalli Christopher , Thrasher David , Al-Qabandi Salman
Published: December 2007

Reservoir souring often occurs as a result of secondary recovery using water-flood. Until recently, the mechanisms of souring were poorly understood but it is now possible to quantify and profile the development of sour gas production.

The latest understanding of the mechanisms of reservoir souring have been used to model the souring potential of North Kuwait reservoirs, undertaken as part of a process of risk management in field development planning.

The Kuwait Oil Company has taken this one step further by interfacing the souring model to a proprietary, state-of-the-art, steady state process simulation package, as part of a wider process of integrated field development. Interfacing a sub-surface souring model to a process facilities compositional simulation has resulted in the ability to assess, with an unusual degree of confidence, the technical and economic effects of reservoir souring on facilities design and operation. This knowledge has been used for the preliminary assessment of options for controlling souring in the future.

To assure accuracy, the proprietary process simulation software thermodynamic generator, chosen for its ability to handle hydrogen sulphide, was independently validated by the thermodynamics section of BP Research Centre.

This paper reviews the basis of the reservoir-souring model and shows the results obtained in terms of sour gas profiles predicted over a period of time. It then goes on to show in more detail how these results were linked into a process simulation model which was constructed to emulate both existing and future facilities configurations.

The paper concludes by showing how the knowledge gained has allowed optimum decision making regarding the materials and equipment of the non-sour service facilities and the safety of operation. In addition, how this knowledge has been used for providing assurance and guidance for the planning of future production facilities.
The Development Process; Zubair Reservoir, Raudhatain Field
Authors: Dashti Hussain , Morrison Neville , Nemcsok Steve , Qazi Anees , Matar Bader
Published: December 2007

This paper describes the process adopted, and results achieved, to provide an interim field development plan for the Zubair reservoir. This is a major oil-producing horizon of the Raudhatain field in northern Kuwait. The multi-billion-bbl reservoir comprises four major producing sandstone units, each with different fluid and rock properties. The strategic intent set in 1995 required that the offtake essentially be doubled within the next 10 years through the implementation of a field waterflood development plan. Teams were established to collate the data and populate electronic data bases. The data from 21 new wells drilled after the liberation of Kuwait was integrated. A sedimentology study of the available core data was completed. A multi-disciplinary team was established in late 1996 to interpret the static and dynamic data and recommend the initial forward development strategy. Evaluation of the data, using classical analysis techniques, confirmed that a peripheral flood program could be implemented and provided an assessment of waterflood performance. Productivity and injectivity were estimated to provide a provisional assessment of wells needed. Ranged production profiles, required for planning, were generated quickly using analogue field data. Prioritization for water injection was established based on required offtake and dynamic performance. Recommendations for the locations of new development wells, incorporating the presence of tar mats and a gas cap, were made together with an adequate surveillance plan to assess the impact of the waterflood.
Modeling and Scale up Of A Heterogeneous Reservoir; Wara Sand, Greater Burgan Field
Authors: AL-Enezi Khalaf , Hsie James C
Published: December 2007

Reservoir studies of large fields with multiple pay zones and complex geology usually require considerable computer resources, manpower, and time. Conventional finite difference simulations offer the best technical justification provided sufficient grid resolution can be employed to define reservoir heterogeneity. Even though significant enhancements hardware has made simulation tasks of large models easier today, the 3-D simulation of full field fine grid models is rarely feasible, because of hardware limitations and extensive history matching requirements.

An approach based on detailed geostatistical characterization of the reservoir properties and a simplified flow calculation procedure was used to construct and scale up a 10.6 million cell geostatistical model to a 300,000 cell simulation model for the Wara reservoir in the Greater Burgan Field. Multiple geostatistical models were generated with different realizations and a representative model was selected based on probabilistic considerations. The fine grid model was scaled up by solving single phase flow equations for all x-z and y-z slices to characterize the reservoir flow parameters such as breakthrough time and fractional flow of oil. Non-uniform coarsening of the fine layers and areal grids was then made to match these flow parameters. The scale up of the permeability values is based on a homogenization procedure and the remaining static properties are calculated using pore volume weighting.

This paper demonstrates the merits of the scale up procedure to adequately capture the complex geology and heterogeneity of the reservoir and yet to retain critical flow characteristics in the coarsened model. It also discusses the limitations of the technique including the introduction of artificial discontinuities in the model and the procedure developed to incorporate over 100 faults, which need to be generated externally. The procedure can be employed to construct simulation models of giant Middle East reservoirs with adequate grid resolution and modest computer resources.
Identification of a High-Producing Ratawi Reservoir Extension in Wafra Field Using 3-D Seismic Data
Authors: Waite M. W. , Weston J. R. , Davis D. W. , Pearn C. J.
Published: December 2007

The Wafra Field is located in the Partitioned Neutral Zone between Kuwait and Saudi Arabia. The field produces oil from the Ratawi Oolite reservoir, which has been under production since 1956. Barriers to fluid movement have severely restricted aquifer support to the overlying carbonate grainstone reservoir, leading to production-induced pressure depletion and low recovery rates. Creative integration of 3-D seismic aspects, well log stratigraphy, and engineering analysis reveal an unexploited reservoir extension which is more open to aquifer support. Wells drilled along this extension are expected to yield higher initial production rates and longer sustained production. The model was used to drill two successful step-out wells that have increased field production by over 12,000 BOPD. Eight of ten additional wells have now been drilled as a follow-up to this success. This paper reviews the case history with a focus on the multidisciplinary integration that led to opportunity identification and exploitation.
Fracture Modeling as a Key to Waterflood Development of the Fahud Field Natih-E Reservoir
Authors: Nicholls C. A. , Boom W. , Geel J. , Al Khodori S. , Al Lawati M.
Published: December 2007

The Fahud field is the largest oil field in Oman. Since its discovery in 1964, this giant carbonate field has gone through a varied production history including an unsuccessful early period of water injection. Since 1984, the field has been produced under Gas-Oil Gravity Drainage (GOGD). The efficiency of GOGD is dependent on an extensive fracture system into which the matrix oil can slowly drain to be recovered from a fracture oil-rim. Since the early 1990's extensive horizontal drilling in the field has provided a wealth of data which is gradually revealing the characteristics of what is a highly heterogeneous fracture system. From the analysis of well performance, mud losses and borehole image data supported by structural geological data, several areas and units within the Natih reservoir are now recognised as sparsely fractured and hence are inefficiently drained under the current GOGD recovery mechanism. This paper describes the data used to construct a fracture model for one such layer, the Natih-E, in Fahud NW. The model has allowed the identification of the most prospective area and units for a matrix waterflood incorporating the results of two waterflood pilot cells. The optimum well pattern for a waterflood development within two of the Natih-E subunits is proposed based on simulation results. The development is expected to provide an increase in recovery from 17% under a GOGD scenario to 40% for the waterflood. This is a clear example of how two different recovery mechanisms, GOGD and waterflood, can be used concurrently in one field to optimise recovery.
Justifying a Full Field Rationalisation: Preparing the Yibal Field for the Next 30 Years
Authors: Eckford Paul
Published: December 2007

The strategic position of the mature Yibal field within Petroleum Development Oman (PDO) is to sustain the company production levels and growth aspirations with a high rate of low cost oil for a prolonged period. The plans discussed in this paper are focused on how Yibal can become a world class operation, covering the full range of HSE aspects whilst fulfilling this mission. Yibal production facilities will be expanded by 50,000 m3/d, and a number of facilities and flowline rationalisation options have been investigated. A capacity expansion and a progressive transformation from the four existing gathering stations to one single gathering and processing station at Yibal A has been selected as the best option, and will be implemented in the near future. A key aspect is the retiring of existing gas lift facilities in favour of ESPs. The combined expansion and rationalisation project will contribute significantly to Yibal's value, in addition to making a large step-change in environmental performance and allowing strategic opportunities for future growth in the area.
Deterministic Reservoir Simulation Approach for Targeting New Wells in a Reefal Mature Field
Authors: Nosseir Mohamed A. , Khairy Aly M. , Heikal Salah A. , Tantawy M.
Published: December 2007

The Ras Fanar Field is a Reefal Limestone of the Miocene age. It is characterized by high porosity and permeability with random local hetroginities.

The field undergoes a strong acquifer support with a developing secondary gas cap which together with the variations in field lithology results in a very un-uniform fluid movement. Water coning and gas channeling took place in different wells at different parts of the field which disturbed the field production, and created unequally depleted areas that can result in spots of bypassed oil.

A multidisciplinary study was therefore conducted to have a better field understanding, and simulate the fluid movement in the reservoir to optimize the drainage pattern, and maximize recovery.

The work initially required the preparation of a firm database for various fluids movement. A successive set of maps was then constructed that defined precisely each fluid movement. The water level map was built to trace the rise of the OWC at different parts of the field. It showed areas of severe water coning, and those of homogeneous water rise. Similarly a gas level map was constructed showing the extension of the developing secondary gas cap across the field. Using both water and gas level maps, together with the structure contour map, an integrated composite map was constructed. A thorough interpretation of this map, finally leads to the oil leg map.

The oil leg map simulated the current reservoir status. It clearly revealed areas of extensive depletion, and those of high oil potential that were candidates for new infill wells. The work has been confirmed by a reservoir simulation study conducted later, which gave similar potential areas. The work integrity was finally confirmed by drilling four infill wells in those areas that proved to be a complete success.

In summary the work was conducted in about three months time. It has been the result of a close co-operation of multidisciplines including (engineers, production geologists, geophysicists etc..) which resulted in an integrated plan for efficient field development.
Experimental Investigation of Some Properties of Emulsified Acid Systems for Stimulation of Carbonate Formations
Authors: Bazin B. , Abdulahad G.
Published: December 2007

Acidizing treatments in carbonate formations is of paramount importance to restore or to stimulate the near-wellbore area by creating wormholes. Emulsified acid was found to be especially effective when the injection rate is low. This paper discusses the properties of some emulsified acid formulations.

The systems used in the study are mixtures of acid, diesel oil, surfactant and possibly a cosurfactant. Model systems made of anionic and nonionic surfactants are compared to the properties of a commercial emulsified acid. Experimental results are focused on the effect of the acid to oil volume ratio, the acid concentration and the surfactant nature. Rheological properties and temperature stability of the emulsion systems are analysed. Results of coreflood tests in limestone samples are presented which compare the behaviour of emulsified acids to the behaviour of plain HCl acid.

It is shown that emulsified acids are effective stimulation fluids at low flow rates: their main advantage is a deep penetration in conditions where plain acid gives compact dissolution patterns. On the opposite, at high flowrates, plain HCl gives better results. These results are confirmed by CT scanner tomography analysis showing highly branched wormhole structures even at low flow rates.

Guidelines are deduced to improve acidizing treatments in low permeability carbonate reservoirs.
Produced Water Management - Reservoir and Facilities Engineering Aspects
Authors: Evans P. , Robinson K.
Published: December 2007

Produced water management via injection, to disposal zones or re-injected into the source oil zone (PWRI), is being increasingly regarded as the best practicable environmental option - far preferable to discharge to the sea or evaporation ponds in the desert.

However, underground injection is not without its dangers and reservoir fracture control is a vital issue for many projects. The planning for and control of injection, either above or below fracture pressure, requires good, project-specific data on water quality and rock properties as inputs to injection simulation programs. Even so, these programs are currently subject to intensive research, especially for soft sands, layered formations and horizontal wells.

Research is on-going too in the areas of damage mitigation and stimulation of PWRI wells, and well failures do occur. In consequence, it is necessary to adequately monitor both well performance and injection water quality, and have in place contingency plans in case of a failure of the injection system. On-line monitoring of water quality may help avoid well damage/failure, and may also enable the upstream separation processes to be operated at their highest efficiency.
Practical and Efficient Approach to Construct a Detailed Full Field Model for Giant Field
Authors: Al-Hasan A. H. , Al-Awami F. H. , MohammedAli M.
Published: December 2007

Managing giant fields to meet certain objectives requires building three-dimensional full field models. However, because of the current software and hardware constraints, modeling must be approached differently. This technical paper presents the methodology and plan to develop a detailed full field finely gridded model for such a giant field.

The simulation modeling plan consists of the following four phases:

Phase I

Construction of a Base Model and utilization of coarsely gridded models covering the entire reservoir and the aquifer. These coarse models are used for global history matching and modeling the aquifer size.

Phase II

Development of four Areas of Interest (AOI) models covering the four areas of the field (North, Saddle, Central and South).

Phase III

Incorporation of all the history matching changes from the AOI models into the Base model. This model can be launched on a Massively Parallel Processing (MPP) simulator.

Phase IV

Integration of the reservoir simulation model with a surface facility network.
Experiences in Permeability Calculations in the Obayied Field (Egypt) Using Magnetic Resonance Imaging
Authors: Oraby Moustafa , Habib El-Sayed , Negm Ehab
Published: December 2007

Permeability is a key factor in well completion in many reservoirs all over the world. The dependency of permeability on the accurate determination of reservoir total and effective porosity, irreducible and movable fluids and the correct correlation between the pore throat and the pore body made it a real challenge. The capability of the Nuclear Magnetic Resonance to provide effective and total porosity, capillary bound fluids and movable fluids provides means for better estimation of rock permeability.

Magnetic Resonance Imaging Log (MRIL) was run in two cored wells in Obaiyed field in Egypt to determine the variation in rock permeability to better design well completion program and select best perforation intervals.

Obaiyed field is a gas sandstone reservoir with low porosity ranging between 5 to 10 porosity units. Obtaining a reliable permeability in this reservoir faced two challenges; the first due to the reservoir heterogeneity while the second due to the drilling mud.

The reservoir rock is heterogeneous and varies from very fine, fine to coarse-grained sandstone. The coarse grained sands represent the high permeability zones, which are imbedded within the fine-grained sand. The key issue in this reservoir is to determine the locations of these high permeability zones within the fine-grained sand beds for well stimulation planning. The determination of the T2 cut-off for both the fine and the coarse grained sands, which vary with depth due to the reservoir heterogeneity, generated a great challenge in determining the formation permeability. A function depending on an average of the T2 distribution is developed to provide the segregation.

The wells in Obaiyed field are drilled with oil base mud with very long relaxation time T1 that even exceeds the gas relaxation time. This property of the oil base mud, if it is not taken into account in logging and interpretation, makes it difficult to obtain a reliable porosity since the NMR will under-polarize the invading OBM as well as the residual formation gas. The time domain analysis technique (TDA) was used to overcome this problem.

In this paper, our experiences in such complex situation is discussed, core analysis is provided, core to log calibration in two wells is presented and recommendations for future applications in Obayied and other similar fields are suggested.