bluuebunny/crossref_metadata_2025 huggingface dataset:
Changing the Value Equation for Underbalanced Drilling
Authors: Davidson I. , Medeiros R. , Reitsma D. , Selby B.
Published: December 2007

The value of underbalanced drilling (UBD) and completion technology lies in several distinct areas. These include improvement in drilling performance by, for example, reducing losses or differential sticking, or increasing rate of penetration or even depletion of troublesome high-pressure zonesi. UBD is also used to improve production rates and increase ultimate recovery. In these cases, UBD has been applied to avoid formation impairment and thus to enhance well productivity. Recently, some operators have recognized that value can also be created through gathering and interpreting reservoir data while drilling underbalanced. This information is used to improve reservoir knowledge and consequently enhance reservoir management.

In low-cost drilling environments, such as land operations in the Middle East and USA, UBD drilling-enabling savings are often marginal and the cost of UBD operations becomes a blocker for wider implementation. The extra cost of UBD acts to discourage a company from fully evaluating the technology's capabilitiesii, even following technically successful trials. In addition, historically the Well Engineering community has championed UBD programs often with scant involvement from the subsurface Petroleum Engineering (PE) disciplines.

Petroleum Development Oman (PDO) operates in such a low-cost drilling environment. PDO commenced UBD campaigns in 2002 with the primary goal of enhancing production and has succeeded in sustaining UBD operations by making significant progress both in reducing costs and increasing the value of information derived from UBD to the Petroleum Engineering organization. This has created the opportunity to more fully evaluate the technical and economic benefits that UBD can deliver and the possibility to deliver cost-neutral UBD wells.

This paper describes some of the challenges faced when initially introducing UBD and the step-by-step approach followed by PDO in Oman and Shell Exploration & Production Co. (SEPCo) in the USA to widen its implementation to other fields. The paper underlines the need for integrated well engineering and petroleum engineering teams in UBD and confirms the pivotal role of sub-surface engineers in interpreting and using the additional and complementary reservoir data that becomes available during UBD. The paper also analyses more closely the actual cost of UBD and provides a balanced perspective on the longer-term UBD value equation.
Underbalanced Drilling in Canada: Tracking the Long-Term Performance of Underbalanced Drilling Projects in Canada
Authors: Kimery Dave , McCaffrey Matt
Published: December 2007

The development of underbalanced drilling (UBD) for production enhancement has advanced significantly since the advent of this technology in the early 1990s. The basis for the initial judgment as to the success of a UBD campaign was usually limited by the information that was available at the time of project completion: project execution success and initial production rates. However, the full scope of the effect of UBD on the overall economic success of a project remains unknown for many cases. While several underbalanced field developments have sufficient production history, drilling records, and cost data available for analysis, to date the body of published literature lacks thorough, long-term case histories.

This paper addresses this scarcity by analyzing several UBD projects in the Western Canadian Sedimentary Basin. The discussion includes a comparison of UBD and completed wells with the offsetting conventional producers in the same reservoir. Comparative analysis using industry-standard decline analysis and economic techniques yield technical and economic insight. To provide a balanced picture of the economic benefits that UBD can bring, both successful and unsuccessful projects are examined. The unsuccessful cases are analyzed to determine the reasons for underperformance, whether they fall into the categories of poor candidate selection or sub-optimal execution.

Understanding the magnitude and the driving factors behind the success and failure of UBD projects is critical to the growth and acceptance of the technology. This paper attempts to assist in that understanding and provide a benchmark for thorough comparisons of UBD case histories for the future.
Hydraulic Optimization of Foam Drilling For Maximum Drilling Rate
Authors: Kuru E. , Okunsebor O. M. , Li Y.
Published: December 2007

The theory of hydraulic optimization of drilling with conventional (incompressible) drilling fluids is well known and has been widely practiced in the industry.

Classical theory of hydraulics optimization for maximum drilling rate calls for either the use of empirical correlations or the use of optimization theory to maximize some arbitrary objective functions such as maximum bit hydraulic horsepower or jet impact force.

Concept of hydraulic optimization for maximum drilling rate when drilling with foam, however, is not well investigated. Compressible nature of the foam makes the use of conventional optimization theory difficult.

A transient-mechanistic model of cuttings transport with foam has been developed and numerically solved recently. In this study, the new model has been used to re-visit classical theory of hydraulic optimization (i.e. maximum bit hydraulic horsepower/jet impact force criteria).

A new methodology has been suggested to determine optimum gas/liquid injection rates for maximizing drilling rate when drilling with foam while keeping the bottom hole pressure minimum.

The new method can be easily used in the field to determine best combination of gas/liquid injection rates and total bit flow area (i.e. jet nozzle sizes) such that maximum drilling rate is achieved.
Optimal Production Management in Unconsolidated Mature Sandstone Environment
Authors: Mufarji S. S.
Published: December 2007

Proposal

In matured unconsolidated clastic hydrocarbon formations there are several factors which contribute to production declines. One of the major factors that significantly impairs inflow into the welbore is solid fines particles which if not managed appropriately can jeopardise hydrocarbon productivity hence prevent maximum/plateau production maintenance.

This paper, presents a new and unique technique which incorporates a combination of a CFD and 3D reservoir simulation approaches to study conditions leading towards pore blocking, characteristics of the damage. Based on the analyses results, optimization suggestions are given. This approach eliminates today's core flood limitations which keep us away from being capable of reducing or avoiding pore plugging damage. The limitations include: inability to inject hydrocarbon gas in a multiphase laboratory test, non-representative nature of core sample size, sample conditions being different from reservoir condition, the questionable applicability of scaling up to field extent and so forth. Hence based on these limitations, there is a need for better pore blocking characterization techniques in risk assessments.

Results suggest that in high permeability sand, the finer the grain size (10 -100microns) the lesser the pressure decline rate. On the other hand, when 150 - 200 microns fines were simulated, the decline in pressure was comparatively more. The sensitivity of grain size in tighter formation is less compared to that found in more permeable formations as in the letter, higher magnitudes of permeability decline were revealed in which case a shallow invasion mechanism was likely. Unlike the grain size influence to pressure drop and permeability decline, the simulated fines concentration ranging from 20% to 50% by volume did not have significant impact. As far as water cut sensitivity is concerned, significant difference in permeability drop was observed between 0% and 10% water cut at fixed fines concentration.
Creative Combination of New Coiled-Tubing Technologies for Stimulation Treatments
Authors: Boumali A. , Wilson S. , Amine D. M. , Kinslow J.
Published: December 2007

Combining multiple tools or processes can provide creative answers to old problems. An Algerian well was producing from two perforated intervals. The upper zone was previously fractured; the lower zone was underperforming. Stimulation treatment using a hydrofluoric-based acid system was designed for the lower zone to significantly increase the well production. Although there was confidence in the stimulation design, certain operational challenges needed to be addressed. To maximize the economics, the workover operation had to be rigless. The decision was made to use coiled tubing with a newly designed through-tubing inflatable packer to mechanically isolate the zone and deliver the harsh fluids required for the stimulation. The next challenge was setting the packer in a 3-m window between the two zones. If the packer were not correctly positioned the treatment, undeniably, would be misplaced. A wireless casing collar locator (CCL) with pump-through capability was chosen to provide accurate, real-time depth readings prior to setting the inflatable packer in a modular combined tool string.

The designed workover required only a single trip in the well, and the production tubing did not have to be retrieved. With the creation of a real-time correlation log, the inflatable packer was set on depth, and the hydrofluoric-based acid system was pumped into the underperforming zone. Post treatment, the oil production more than tripled. Two technologies were combined in an innovative application that met all operation objectives.
Selecting Ultra-Lightweight Cement for Effective Casing Protection and Hydraulic Isolation: A Case Study
Authors: Fujita K. , Minobe M. , Imazato M. , Johnson C. , Abbas R. , Ucucu A.
Published: December 2007

Lost circulation is a common problem in the massive waterbearing Palaeogene and Cretaceous carbonate formations that extend across all United Arab Emirates fields and the Gulf countries. Traditionally, these formations are drilled with water, 8.10-lbm/gal emulsion mud, or 7.9-lbm/gal aerated mud to minimize losses. Once the 13 3/8-in. surface casing is run, the main objective is to protect it against corrosive brines in carbonate formations and formations at shallower depths. To meet this objective, complete casing-cement coverage all the way to surface must be achieved. Some methods to ensure complete casing cement coverage have been ineffective. These methods included using conventionally extended cement slurries as low as 12.6 lbm/gal, using a stage collar to execute the cementing operation in two stages, and performing remedial, top -down cementing operations after completing the primary cementing operation. Because these methods were ineffective, cemented casings often had major corrosion problems that reduced the life of the wells.

This paper describes the design and results obtained from the first successful use of high-performance, low-weight slurries (HPLWS) and a new ultra-lightweight cement system (ULCS) to cement surface and intermediate casings for Bunduq Oil Co. offshore Abu Dhabi.
An Experimental Approach of the Reversibility of Asphaltene Deposition under Dynamic Flow Conditions
Authors: Shedid S. A. , Abbas E. A. A.
Published: December 2007

Occurrence of asphaltene deposition in producing formation constitutes one of the most serious problems currently encountered in the petroleum industry in many areas of the world. Reversibility of asphaltene deposition represents crucial argument and controversy in laboratory research of the petroleum industry. Deep understanding of this phenomenon is the key for treatment the problem of asphaltene deposition.

The major goals of this study were to investigate (1) asphaltene adsorption rate on carbonate rock surfaces under static condition, and (2) asphaltene deposition and its reversibility under dynamic flow conditions. For the sake of achievement these goals, two groups of experiments were undertaken. The first one measured asphaltene adsorption rate under static condition while the second group was devoted to study reversibility of asphaltene deposition under dynamic flow condition through actual porous medium.

The results of the study indicated that the increase of aging time increases asphaltene adsorption on carbonate rock surfaces under static condition. However, the major part of asphaltene is adsorbed during the early thirty hours of the first contact of oil with rock surface. The results of dynamic flow experiments showed that asphaltene deposition is a continuous process causing permeability damage and is also partially reversible. Furthermore, the asphaltene deposition causes more damage in low permeability rock than that one in higher permeability. The obtained results are expected to have important implications for better formulation of treatments of asphaltene deposition.
Casing Directional Drilling Using a Rotary Steerable System
Authors: Strickler Robert , Mushovic Todd , Warren Tommy , Lesso Bill
Published: December 2007

The hardware used in casing while drilling operations over the past 5 years has proved to be robust and reliable. Several directional wells have been drilled successfully with casing using positive displacement motors (PDMs), but the drilling efficiency was significantly degraded in most of them. This paper documents the drilling of the first two wells to utilize a rotary steerable system (RSS) to improve drilling efficiency when drilling with casing.

Combining an RSS with casing while drilling operations seemed to be a natural way to eliminate the major weaknesses in motor bottomhole assembly (BHA) designs. Rotary steerable systems had not previously been used with casing while drilling because both are new technologies focused on different environments. Casing while drilling developed on land operations while rotary steerables have been popular for offshore projects.

ConocoPhillips has drilled more than 94 wells in the Lobo trend of South Texas since 2001 using the new technique. As part of a technology demonstration project to accelerate the technology to offshore applications, two wells were drilled with an RSS.

The first was an operational test conducted by drilling vertically with the RSS. The second was a full directional test o with a build to 29° directional turn. and then a drop to vertical, including a 100°
How Integrated Well Planning, Technology, and Operations Excellence Impact ExxonMobil's Development Well Results
Authors: Newman Harry E. , Roberts Charles M. , Biegler Mark W.
Published: December 2007

This paper discusses ExxonMobil's approach to designing and drilling world-class development wells. In today's business environment, proper well design and flawless execution are essential as our investments increasingly rely on fewer, more complex, very large volume wells. To achieve success, ExxonMobil has always treated drilling as a core business. This means we value this area of expertise and hire, train, and retain this job skill to contribute to the success of what we do to provide value for our shareholders. We focus on a disciplined approach to drilling and completion investments, full leveraging of our global knowledge, development and deployment of people, technical solutions that balance minimum cost/appropriate risk and full-life-cycle capability, and flawless execution.
Through Bit logging: Applications in Difficult Wells, Offshore North Sea
Authors: Runia John , Boyes John , Lodder Robert Jan
Published: December 2007

Through bit logging is a method for data acquisition using the drill string and bit as a conduit to the well bore.

Two case studies are presented demonstrating the unique capabilities of this technology to obtain data in difficult and troublesome well situations. Both cases were recent (early 2004) wells, offshore North Sea.

Case study 1 concerns an exploration well with a large open salt interval open above the reservoir. Conventional logging tools could not pass the squeezing salt interval, and TBL was used to get past the troublesome interval and successfully obtain quad combo and pressure data. Subsequently, the cement stinger could not pass the same interval, and the TBL bit was again used, this time to cement through.

Case study 2 describes a well drilled into a nearby block, suspected of being depleted. After loosing the BHA, the operator wanted to reduce the risk of getting stuck with an RFT and decided to use TBL to successfully obtain wireline pressure data in the subsequent side track.

Recent developments include a new type of Side Entry Sub System to enable easy surface deployment as well as providing a rapid easy fishing method in case the logging tools were to get stuck during TBL operations.

Compatibility with rotary steering and MWD is under development, delivering the concept of ‘Through Bore Drilling’, the ultimate low cost drilling system. This will allow directional drilling in combination with open hole logging and other operations through the bit, in a single trip.

Conclusion: TBL opens up new low cost/low risk options for data acquisition (and other through bore operations) during well construction. It gives both drilling and petroleum engineers new and low cost options to choose from to optimise well construction and data acquisition. TBL is a first significant step on the way to Through Bore Drilling and has already proven its versatility in a number of ‘difficult well’ cases.
Deepwater Batchset Operations Through the Magnolia Shallow Water Flow Sand
Authors: Eaton Luke F. , Actis Stephen C. , Williamson Roger N. , Vernier Charles G. , Long Jeff
Published: December 2007

ConocoPhillips is developing the Magnolia field with a Tension Leg Platform (TLP) in 4674 ft of water in Garden Banks (GB) block 783 in the Gulf of Mexico. Three wells were drilled at the eventual TLP site to discover and appraise the field prior to sanction of the development plan. Field development plans required drilling an additional six wells at the TLP site where a shallow water flow (SWF) zone is present. The development plan included batch drilling and casing the SWF interval prior to deepening any of the wells to total depth.

The Magnolia batchset program was successfully conducted in 2002 using the Ensco 7500 dynamically positioned semi-submersible drilling vessel. The six well batchset program was drilled at less than the Authority For Expenditure (AFE) cost estimates with zero lost workday cases.

The batch set program included jetting 36 in. casing to 246 ft below mudline (BML), directionally drilling a 26 in. hole to 3264 ft BML while building hole angles up to 17°, and running and cementing 20 in. casing with verified cement returns to the mudline. The SWF sand interval was drilled and cased without "Top Setting" a cemented casing string above the SWF zone. Although individual exploratory wells have been drilled and cased without top setting casing previously, the Magnolia field is the first deepwater field with a SWF zone to be developed in this manner.

Pre-planning for the SWF zone addressed directional drilling issues, water base mud (WBM) design, cement formulation and placement procedures, and logistic supply to the drilling rig. Each well required three 89 ft joints of 36 in. casing, 81 joints of 20 in. casing, 40,730 bbls of blended WBM, and 6,760 ft3 of cement. Five supply vessels were used to provide logistic support for the operation.

This paper will focus on the extensive planning process and the operational aspects of performing a batchset drilling program through a SWF sand in a deepwater environment.
A Conceptual Sensory System for Cross Hole Reservoir Characterization Using a Pair of Horizontal Wells
Authors: Al-Anazi A. , Ershaghi I.
Published: December 2007

This paper presents a new approach for testing and analysis of pressure interference between horizontal wells for mapping heterogeneity of interwell flow systems. The proposed sensor network requires multiple isolated pressure sensors in one of the horizontal wells (the observation well) with synchronized data recording. Using a new derivation, based on integrated and multiple point source formulation, the analytical model to interpret the responses at various nodes of the sensor network has been developed.

The new analytical formulation models the performance of various point source recorders on the observation well based on the Kelvin's point source solution. While the pulsing horizontal well can have its entire completion interval active, each sensor in the observation well is assumed mechanically isolated from the other sensors while receiving transient responses in the immediate domain of its influence. Synchronized responses received at the sensors, are then analyzed to detect preferential trends in transmissivities. Calibrated test with numerical reservoir models have been conducted to validate the synchronized response model.

The proposed approach is an improvement over the previously published interference models between horizontal wells where the active and responding wells are assumed as fixed line sources without being able to take advantage of multiple sensors in the observation well.

The analytical pressure solution, as validated by numerical solution, provides the opportunity to detect flow channels during single phase flow and dynamic fluid-fluid interfaces by time lapse repeat monitoring.
Controlling Cement Operations from an Onshore Operation Center
Authors: Tyberø P. , Allen B. , Helgesen J. T.
Published: December 2007

Driven by industry trends to deliver real-time solutions as well as the high costs to produce hydrocarbons from the mature North Sea fields, a global operator and a global service company have worked together to successfully complete the first fully remote-controlled, offshore cement operation from onshore. By combining proven technology with a specific vision for future operations, this next step in propelling the industry toward the possibility of remote-driven operations was completed on April 27, 2004.

This paper will detail the vision and business cases behind the onshore operation center, remote-controlled cement equipment, and movement of cement operations to the onshore location. It will also present the benefits of controlling cement operations remotely and onshore as it pertains to the working environment in the Norwegian sector of the North Sea. This achievement has proven that remote operation of drilling equipment is a fully feasible and reliable solution, and it has paved the way for further remote operations.
Hibernia Record Well Breaks Extended Reach Drilling and Completion Envelope
Authors: Elsborg Carsten C. , Power Adrian K. , Schuberth Paul C.
Published: December 2007

In 2002 the Hibernia Management and Development Company (HMDC), led by ExxonMobil Canada, embarked upon the development of the northern most compartment of the Hibernia development project, (‘A’ Block). To access these reserves, it was proposed to drill and complete a 31,000 ft measured depth (MD) oil producer with a horizontal departure and vertical depth that would exceed the present day industry extended reach drilling (ERD) envelope.

Successfully drilling this world-class well would require the application and extension of currently available drilling and completion technology. Meeting the project goals would demand the installation of a large monobore completion system with offshore-Canada's deepest downhole telemetry system. The proposed trajectory would require management of weak and unstable intervals across an extended 17,000 ft MD intermediate section. This trajectory would necessitate the installation of record length production casing strings under high friction load. Subsurface tool reliability under extreme cyclic loading would be needed, especially at the lower wellbore sections where downhole tool failures would be costly due to depth and trip time. The project would require the development of effective strategies to mitigate very high circulating pressures and fluid rheology at extended distances. Drill pipe and tool joints would require upgrade to meet the higher anticipated loads for this program. Completion equipment would also require significant enhancements to meet the pressure and axial load requirements of the wellbore. Planned intervention tools would require modification to allow passage through the extended reach sail angle. Wellbore tractors would be refitted and shop testing would be conducted to ensure all tools were ready for application.

To meet these challenges HMDC would leverage existing local experiences1 while at the same time engage recognized international expertise to supplement existing practices. Technical work sessions were conducted during the planning phase to start the communication process to all stakeholders (including service providers) and to identify critical technical boundaries and key technologies to extend the current ERD envelope. The comprehensive review and upgrade of Hibernia ERD practices was effected through external engagement of ERD experts for worldwide lessons learned. Internal resources were accessed to effectively integrate the latest concepts in hole cleaning and wellbore stability. All the while, operational and design revisions were based upon, and complemented by, successful existing Hibernia ERD practices.
Using a Combination of Cement Systems to Defeat Severe Lost-Circulation Zones in U.A.E.
Authors: El-Hassan H. , Abdelrahman M. , Johnson C. , Belmahi A. , Rishmani L. , Jarouj H.
Published: December 2007

The primary objective of cementing an oil or gas well is to provide good zonal isolation between different formations that have been penetrated by the wellbore. Cementing across weak formations with a low fracture gradient usually leads to poor cement coverage, which makes zonal isolation difficult or impossible.

Abu Dhabi Company for Onshore Oil Operations (ADCO) recently had this problem in the water-bearing Palaeogene and Cretaceous carbonate formations that extend across all United Arab Emirates fields and the Gulf region. Several techniques have been used in the past to bring high-quality cement up to surface to protect casing from corrosive brines. These techniques include using multistage tools, pumping conventional lightweight cement to execute the cementing operation, and performing a remedial, top-down cement job after completing the primary cementing operation. Mixed results demonstrated the limitations of these techniques.

Today, with a better understanding of the problem of cementing in these formations, a unique, cost-effective process has been developed to ensure that cement coverage goes up to surface. Essentially, it combines a sequence of three slurry systems, including a novel, ultra-lightweight cement technology, to defeat the severe lost-circulation problem and achieve complete zonal isolation. This paper describes the design and results obtained from the successful application of this new process to cement casings in formation where severe lost-circulation problems are likely to occur.
Unique "Through Tubing" Completions Maximize Production and Flexibility
Authors: Johnson Mark O. , Hyatt Paul G. , Stagg Ted O. , Gantt Lamar L.
Published: December 2007

The challenge with through tubing sidetrack completions has been dealing with small clearances and the lack of ready-made equipment. Over the last 10 years and 450 coiled tubing drilling sidetracks on Alaska's North Slope a number of unique completion designs have been developed to maximize production and achieve vertical/zonal isolation. These completion techniques are now proven, and may make lower cost through tubing sidetracks more feasible for other mature fields.
API Specification 5CT N-80 Grade Casing May Burst or Part Unexpectedly if Supplementary Metallurgical Requirements are not Specified
Authors: Gokhale Samit , Ellis Sean
Published: December 2007

N-80 grade casing is a preferred casing grade for production casing strings. Most often, N-80 casing is ordered to API Specification 5CT without specifying the appropriate supplementary requirements. Casing strings that meet the minimum strength requirements of API Specification 5CT have experienced sudden failures during normal workover and well stimulation operations. This paper presents a case study and lessons learned from the analysis of such a casing failure. The paper is based on the results of metallurgical analyses performed during the investigation.

This paper details the standard manufacturing operations and heat treatment processes performed for N-80 casing ordered to API Specification 5CT, and the result of these operations on the casing's final material properties. By re-heat treating the failed casing with published supplementary requirements in mind, the casing material properties were improved substantially. If the casing initially had the properties of the re-heat treated steel, the failures would likely have been avoided.

Factors that contributed to the N-80 casing failures are presented and the case is made for specifying supplementary tests for verification of fracture toughness.
Implementation of a New Risk Based Well Collision Avoidance Method
Authors: McNair G. A. , Lance S. J. , Codling J. , Watson R.
Published: December 2007

A majority of industry operators and service companies have adopted directional drilling collision avoidance rules based on stringent controls to prevent surface collisions and consequent human and environmental damage. These rules are found to be severely restrictive for the optimal positioning of wells through deeper reservoir zones where the level of damage from collision can be contained.

A new method is proposed that retains existing rules for avoidance of shallow (severe outcome) collisions and provides the option for use of risk based rules in deeper sections of wells where the outcome of a collision would not be as severe. The risk level of collision with respect to any offset well is calculated and then converted to a Risked Clearance Factor, an established standard for evaluating different levels of collision tolerance in wells.

Deep intersections have several characteristics which require separate treatment from shallow intersections. They have high convergence angles which minimize the physical space and distance where a collision may occur and they have lower economic risks of a collision relative to the cost of corrective action.

This method has been implemented in a field area of rapid prospect planning and development. The rules are designed to be simple and practical in order to reduce planning and drilling cycle time. A matrix of risk elements, specific to the field area is presented for different depths of collision to help to derive the level of tolerable risk. A case history is presented that shows the clear benefit of utilizing the alternate method.
Novel Completion Technology Eliminates Formation Damage and Reduces Rig Time in Sand Control Applications
Authors: Garfield Garry , McElfresh Paul
Published: December 2007

Among the highest risks in well completions is formation damage caused by perforating. Fractured and compacted zones, perforation gun debris, and broken formation blockages are common types of damage that can occur inside the perforation tunnel. Reducing or eliminating initial perforation damage can result in a more productive well over its lifetime.

This paper examines a completely new technology for completing wells in unconsolidated formations that installs a liner hanger and sand control mechanism in a single trip to eliminate explosive perforation charges and associated formation damage risk. This new technology was developed by a Joint Investment Project (JIP) that included three major operators, a large service provider and a small technology company. In addition to eliminating perforating, the technology reduces the cost of well construction by allowing the production liner, flow conduit, primary cementing, and sand control tools to be run in a single trip.

The perfless completion system uses telescoping tubes that extend from the liner into the formation by applying hydraulic pressure and mechanical force. Once the tubes are extended (or telescoped), the liner is cemented in place. The tubes, which contain sand control media, form conduits from the formation to the casing ID. No large, high-horsepower fluid pumping treatments are required. Neither are after-completion drilling mud and fluid-loss control measures, both of which can cause formation damage.

The new completion method eliminates gravel packing and minimizes intervention in completion operations, saving substantial rig time. It also simplifies operation logistics, especially in remote or offshore environments.

This paper describes initial field test results of the new system, cost comparisons with existing methods, and expected economic benefits over the lifetime of wells in typical applications of this new technology.
Field Experience: First All-in-One Machine for Making Up Drillstring, Bottomhole Assemblies, Casing, and Tubing in the Norwegian Sector
Authors: Abrahamsen Egill , Trulsen Alf Arne
Published: December 2007

A new-generation, multifunctional iron roughneck was installed and operated on the ULA platform in the North Sea, offshore Norway, in 2003. This iron roughneck is unique in its ability to make up and break out a vast variety of drillstring components without personnel on rig floor, and it accommodates remotely operated power tongs for casing and tubing running by simple exchange of tong modules inside the roughneck carrier. The iron roughneck included such features as a new integrated mud bucket, a cleaning and doping device for drillpipe (tool joint box), and a stabbing guide.

All of these features contributed to a safer rig floor operation, but they also enabled a streamlined interface with rig floor operations without a multitude of control panels and interfaces. The operator initially rented the equipment, which replaces traditional iron roughnecks, for a one-well program but decided to purchase the system for subsequent drilling operations.

This paper discusses the rationale for selection of the equipment for the ULA project; the operator's expectations; installation, interface, start-up, and operational experience from the ULA platform; and success of the equipment in meeting Norwegian authorities' more stringent requirements for remote operation.
Improving the Reliability and Availability of Dynamic Positioning Systems
Authors: Fougere Peter
Published: December 2007

While Dynamic Positioning (DP) system reliability currently is at historical peak performance levels, opportunities exist for additional improvement. The following three improvement areas are based on findings from a review of available DP Event Reports. The first two areas involve Failure Mechanics and Effects Analysis (FMEA), which is the main tool used for assessing equipment reliability. The third finding covers training of DP Operators (DPOs). A review of existing DP FMEAs showed inadequate depth of execution in many cases, while others did not comply with existing industry FMEA standards. A specification was developed to raise the scope and quality of DP FMEAs. The specification will be used to perform new FMEAs on existing vessels. We expect the new FMEA studies will demonstrate higher effectiveness of finding potential DP reliability problems.Utilizing FMEA techniques and our fleet experience, we are preparing Guidelines for Reliability and Availability of power plant and thrusters. They will be used to assess existing systems for upgrade and for the basis of design for any new vessel.Human error accounted for some portion of most DP events. Our assessment showed that the standard industry wide training for DP Operators (DPOs) is not fully adequate. A series of efforts identified what a DPO needs to know, prepared a DPO development plan to match the needed knowledge, and developed a DPO competency assessment scheme.
Applicability of the VAPEX Process to Iranian Heavy Oil Reservoirs
Authors: Azin R. , Kharrat R. , Ghotbi C. , Vossoughi S.
Published: December 2007

The objective of this paper is to evaluate the viability of the VAPEX process for an Iranian heavy oil reservoir according to the reservoir characteristics. Also, based on the reservoir fluid conditions, the optimum solvent system to meet the requirements of the VAPEX process is determined. In addition, a mechanistic model was developed for the study of the VAPEX process by considering the mass transfer and fluid flow mechanisms characteristics of the VAPEX process. The model is capable of predicting the drainage rates of heavy oil in all stages of the process, including the pseudo-steady state. Also, various initial and boundary conditions can be specified to the model. The results obtained by this model agree well with the experimental data. The model was further applied to a fractured system and effects of solvent injection rate, fracture and matrix permeability, matrix to fracture permeability ratio, and initial viscosity of the reservoir heavy oil on the performance of the VAPEX process were studied.
Development of the Ultimate Ultra Harsh Environment Jack-up Drilling Rigs
Authors: Smidth Frederik , Wullf Per
Published: December 2007

Drilling with jack-ups in harsh environments has moved into deeper and deeper water during the last 10 years.

Previously 90 m was considered the maximum whereas up to 150 m water depth is now feasible.

In addition several new features are now available on harsh environment jack-ups which increase the drilling efficiency by up to 25% compared with the more conventional jack-up types.

This paper describes the process of creating the next generation deepwater jack-up drilling rig, and the results and operational experience with the Maersk "I" class rigs-the Maersk Innovator and the Maersk Inspirer.

The Maersk Innovator has been in operation for approximately 18 months and the Maersk Inspirer is in transit to the North Sea. The Maersk Inspirer is contracted to start operating in February 2005.
Upscaling Fracture Networks for Simulation of Horizontal Wells Using a Dual-Porosity Reservoir Simulator
Authors: Ding Y. , Basquet R. , Bourbiaux B.
Published: December 2007

One difficulty in fracture upscaling for field-scale dual-porosity reservoir simulation is the determination of equivalent gridblock fracture permeability, which depends on the type of boundary conditions imposed on the discrete fracture network (DFN) simulation. Actually, classical upscaling procedures are usually based on linearly-varying pressure boundary conditions, which cannot capture the near-well flow behavior. As a result, the well productivity calculated by a dual-porosity flow simulator can be very different from that calculated on a DFN model.

This paper proposes a near-well fracture upscaling procedure based on the geological DFN model to improve the accuracy of well productivity in fractured reservoir simulators. This procedure enables to represent the actual flow through the fractures and the exchanges between matrix and fractures in the well vicinity. Based on the computed near-well flow pattern, equivalent fracture transmissibilities as well as numerical well indices are determined and assigned to the gridblocks of dual-porosity reservoir simulator. Efficiency and necessity of using near-well upscaling procedure are demonstrated by examples.
Sequence Stratigraphy and Reservoir Characterization of the 2nd Eocene Dolomite Reservoir, Wafra Field, Divided Zone, Kuwait-Saudi Arabia
Authors: Wani M. Rafiq , Al-Kabli S. Khalil
Published: December 2007

The 2nd Eocene dolomite reservoir is one of the major producers in the giant Wafra Field of the Divided Zone between Kuwait and Saudi Arabia. The reservoir is of Paleocene age and occurs in the Tertiary Umm Er Radhuma Formation. The reservoir has been producing since late 1950's primarily under depletion drive. Recoveries, however, remain poor (about 5% of OIIP) mainly due to low-gravity oil and reservoir heterogeneity. A geological model that better defines reservoir heterogeneity is a pre-requisite for evaluating and implementing EOR techniques.

Primary porosity in subtidal dolomitized carbonates associated with evaporites, as well as its later modification by dolomitization, dissolution and cementation, typically occurs in multiple zones formed within shallowing upward cycles. This paper attempts to identify such high frequency cycles in the Wafra 2nd Eocene Reservoir and place them in a sequence stratigraphic framework. Based on core analysis, and well log correlations in more than 300 wells, eight high frequency cycles further divided into 15 ‘zones' are recognized. This zonation helps to define the better and poorer reservoir units and the intervening non-reservoirs in a systematic manner as it brings out the distribution of grain rich dolomites and evaporites, as well as the cyclicity of dissolution and cementation. This has helpedin improving reservoir definition over the entire field and led to a more robust stochastic model.
Efficient Three-Dimensional Implementation of Local-Global Upscaling for Reservoir Simulation
Authors: Wen X. -H. , Durlofsky L. J. , Chen Y.
Published: December 2007

Upscaling is often applied to coarsen detailed geological reservoir descriptions to sizes that can be accommodated by flow simulators. Adaptive local-global upscaling is a new and accurate methodology that incorporates global coarse scale flow information into the boundary conditions used to compute upscaled quantities (e.g., coarse scale transmissibilities). The procedure is iterated until a self-consistent solution is obtained. In this work, we extend this approach to three-dimensional systems and introduce and evaluate procedures to decrease the computational demands of the method. This includes the use of purely local upscaling calculations for the initial estimation of coarse scale transmissibilities and the use of reduced border regions during the iterations. This is shown to decrease the computational requirements of the reduced procedure by a factor of about six relative to the full methodology, while impacting the accuracy very little. The performance of the adaptive local-global upscaling technique is evaluated for three different heterogeneous reservoir descriptions. The method is shown to provide a high degree of accuracy for total flow rate, local flux and oil cut. In addition, it is shown to be less computationally demanding and significantly more accurate than some existing extended local upscaling procedures.
Conditional Statistical Moment Equations for Dynamic Data Integration in Heterogeneous Reservoirs
Authors: Li L. , Tchelepi H. A.
Published: December 2007

We present an inversion method for the integration of dynamic data directly into the statistical moments of the dependent variables, such as pressure, for flow in heterogeneous porous media.

We consider the problem of incompressible Darcy flow in a heterogeneous domain. We assume that a few measurements of permeability are available and that the mean, variance, and correlation structure of the permeability field are known. In addition, we assume that a few measurements of the dependent variable, e.g. pressure, are available. The first two statistical moments of the dependent variable (pressure) are conditioned on all available information directly. The approach is based on applying an iterative inversion scheme to integrate dynamic data into the conditional statistical moment equations (CSME). That is, in addition to statistical information about the permeability field, measurements of static (permeability) and dynamic (pressure) variables are used to condition, or improve the estimates of, the mean and second moments of pressure and velocity directly. This is different from Monte Carlo (MC) based geostatistical inversion techniques, where conditioning on dynamic data is performed for one realization of the permeability field. In MC based schemes, estimates of the prediction uncertainty are obtained from statistical postprocessing of a large number of inversions, one per realization.

Our moment-based dynamic data integration method is demonstrated using several examples of flow in heterogeneous domains in a quarter-five-spot setting. We show that as the number of pressure measurements increases, the conditional mean pressure exhibits more spatial variability while the conditional pressure variance becomes smaller. Our experience indicates that iteration of the CSME inversion loop is only necessary when the pressure measurements deviate significantly from the prior (conditional) expectations. We also discuss how the CSME flow simulator can be used to assess the value of both static and dynamic information, measured in terms of reduction of prediction uncertainty.
The Use of Parallel Processing with Dynamic Gridding
Authors: Darche G. , Grabenstetter J. E. , Sammon P. H.
Published: December 2007

There has been considerable interest shown in the use of dynamic gridding techniques for isothermal and thermal compositional simulation. These techniques allow simulation grids to adapt to the physics of complex EOR processes, while retaining a high degree of computational efficiency through the use of relatively coarse grids in areas where there is little activity. Since areas of interest in reservoir models change with time, simulators that use dynamic gridding techniques must be able to deal with changing internal pointer systems as a regular occurrence in their calculations.

There also has been interest in the use of shared memory parallel computers that achieve computational efficiency through the use of various techniques for overall simulator parallelization, as well as for the use of suitable reservoir splittings and associated multi-coloured orderings for ILU linear solvers. These splittings are usually based on some kind of regular cell-based splitting of the reservoir. Unfortunately, such splittings do not immediately apply to the unusual grids generated by dynamic gridding schemes, which exhibit multi- level refinements that are constantly changing.

The goal of this paper is to examine alternate solver orderings based on novel applications of reservoir splittings and also to examine orderings that are applicable to more general systems, such as orderings arising from graph- theoretic notions. The paper will give an overview of different ordering strategies for the parallel linear solver, and will examine how they fare when faced with complex compositional field examples. Results will be shown that indicate that the benefits of dynamic gridding and of the use of a parallel ILU solver can be simultaneously realized in simulations of complex EOR processes. The combination allows for more detailed simulation work and the possibility of working with more reservoir realizations, greatly enhancing the understanding of complex reservoir processes.
Multilevel Fracture Network Modeling of Naturally Fractured Reservoirs
Authors: Kazemi H. , Atan S. , Al-Matrook M. , Dreier J. , Ozkan E.
Published: December 2007

This paper provides a review of common approaches for simulation of naturally fractured reservoirs and a new model formulation that is more amenable to the utilization of detailed geologic information from deterministic models, multipoint statistical simulations (MPS), and discrete fracture network (DFN) models. Unlike the common dual-porosity and dual-permeability models, the new model considers flow in several sets of fractures (that is, micro, macro, and mega fracture levels) and the wells can intercept any class of fractures. Matrix flow is also included in the formulation. A dual-mesh-computing algorithm is used to capture the major orientation of fractures in the flow network. The algorithm consists of the conventional five-point discretization for the coarse grid and a special nine-point discretization scheme for the fine grid. The size of the coefficient matrix for the discretization scheme can be reduced because of the dominance of vertical flow drainage in fractured reservoirs.
An Efficient Formulation for Simultaneous Solution of the Surface Network Equations
Authors: Shiralkar G. S. , Watts J. W.
Published: December 2007

We present a novel formulation for simultaneous solution of the surface network equations, which are cast into a form similar to the reservoir flow equations. This form is more palatable to the efficient solvers already developed for reservoir simulators.