bluuebunny/crossref_metadata_2025 huggingface dataset:
Openhole Stability Analysis of Horizontal Wellbores Under Production Scenarios in Jurassic Carbonate Reservoirs of West Kuwait
Authors: Franquet Javier A. , Verma Naveen K. , Azeemuddin Mohammed , Al-Shamali Adnan , Al-Morakhi Rasha , Reji E. C.
Published: December 2007

This paper presents the results and methodology of the open-hole stability analysis under production scenarios of one horizontal wellbore drilled and two horizontal wellbores planned in Jurassic carbonate reservoirs of West Kuwait. The main objective of the analysis was to investigate the stability of these horizontal wellbores under multiple drawdown conditions and different reservoir depletion scenarios in order to select a suitable completion strategy which guarantees borehole stability during the productive life of the reservoirs.

The stability study includes the mechanical property characterization of the formations and the in-situ stress tensor description of the oil field. The static mechanical properties were obtained from the log responses and petrophysical analysis of several wells around the field by using a micromechanical approach. This approach is based on a constitutive model describing the microscopic processes occurring in a rock sample during tri-axial loading. A postprocessing analytical program for borehole-wall failure prediction and in-situ stress estimation/calibration was used in the open-hole stability analysis. The open-hole stability analysis consisted of predicting the shear failure zone around the borehole wall under production scenarios. When the shear failure zone covers the full extent of the borehole wall, the risk of borehole collapse becomes imminent. Therefore, the maximum drawdown which maintains borehole stability was obtained for each horizontal wellbore as a function of reservoir pressure depletion.

The open-hole stability analyses were also done with multiple compressive strength degradation scenarios in order to address the effect of grain-cement disintegration after acid stimulations. The results of these analyses were found to be useful in evaluating and deciding optimal well completion (open-hole, cased and cemented or slotted/expandable liners) for these wells.
Permeability Modeling Using Neural-Network Approach for Complex Mauddud-Burgan Carbonate Reservoir
Authors: Al-Bazzaz W. H. , Al-Mehanna Y. W. , Gupta A.
Published: December 2007

This paper reports a comprehensive study towards quantitative characterization of the permeability distribution in complex Mauddud-Burgan reservoir in Kuwait. The main objective in this study is to develop a generalized strategy for data-mining a large data-set of rock measurements. This study utilizes measurements of petrophysical and grain/ pore morphology properties in order to correlate permeability. Data-set contain measurements obtained from different length scales, ranging from SEM to wire-line log scale.

Characterizing the permeability for the Mauddud-Burgan reservoir is a challenge because of the complexity of this reservoir. The process is dependant on the type of data available for the reservoir. This study strives toward comprehensive data mining to understand the permeability of this complex reservoir.

A Multiple-Layer Feed Forward, MLFF, with back propagation neural network is developed to calculate the permeability at each desired vertical depth in the reservoir. This tool can assist in determining permeability at any vertical depth of the reservoir, within the boundaries of the reservoir model. Knowledge of other petrophysical properties, such as, porosity, pore type, and pore size distribution, as available, are integrated to estimate the permeability.
Improved Oil Recovery by Application of Ultrasound Waves to Waterflooding
Authors: Amro M. M. , Al-Mobarky M. A. , Al-Homadhi E. S.
Published: December 2007

In oil reservoirs about 60% of the original oil in place remains as residual oil after primary and secondary oil recovery because of geological and physical factors. By means of improved oil recovery methods, additional oil can be mobilized. However, there is no universal IOR method to be implemented in any reservoir. Therefore, efforts are made to develop alternative tertiary methods with lower application risk. One of these alternatives is the application of sound/ultrasound waves in the reservoirs to overcome the interfacial tension between oil and water, resulted in reduction of capillary pressure in the pores.

In this study, laboratory experiments on core samples were conducted to investigate the effectivity of ultrasound waves on mobilizing additional oil. The core flooding was performed horizontally and vertically and the wave stimulation was applied at original oil in place and at residual oil saturation after initial waterflooding. Oil/water relative permeability were calculated to evaluate the flooding performance in presence and absence of wave stimulation and the rate of oil recovery was determined. In addition, water fractional flow curves were considered to determine the average water saturation after breakthrough in presence and absence of ultrasound waves. Moreover, the effect of wave stimulation on unconsolidated core samples was investigated.

Results show that the rate of oil displacement increases due to various identified mechanisms, and the interaction of the generated waves with the fluids in porous media causes changes in relative permeability and in water breakthrough. Wave stimulation at residual oil saturation lead to higher oil recovery than that at original oil in place and therefore, this method is advised to be used in depleted reservoirs. Moreover, wave stimulation on core sample with a compressive strength less than 150 psi (unconsolidated) is not recommended due to sand production.
Multiphysics and Multiscale Methods for Modeling Fluid Flow Through Naturally Fractured Vuggy Carbonate Reservoirs
Authors: Popov Peter , Bi Linfeng , Efendiev Yalchin , Ewing Richard E. , Qin Guan , Li Jianglong , Ren Yulin
Published: December 2007

We present a novel approach for flow simulations through naturally-fractured vuggy carbonate reservoirs. This approach generalizes upscaling methods which have been successfully used to perform reservoir simulations on geological (fine) scales. Typically, vugular porous media is described using both Stokes and Darcy's equations at the fine-scale. We propose the use of simplified model based on Stokes-Brinkman equations. Stokes and Darcy equations can be obtained from these equations by appropriate choice of parameters. Moreover, in the presence of damaged zones between vugular regions and Darcy regions, Stokes-Brinkman equations allow a seamless transition.

The upscaling of fine-scale equations is addressed within homogenization theory. Appropriate local problems are solved to compute the effective permeabilities, which are further used for the simulations on the field scale. We present numerical results for homogeneous and heterogeneous background permeability fields. Our results show that the coarse-scale permeability field is greatly affected when the background permeability is heterogeneous. This is due to the fact that the high flow channels connecting some of the vugs significantly alter the upscaled permeability. We compare the coarse-scale pressure obtained from upscaled equations with the averaged fine-scale pressure. The results are in agreement which indicates that the upscaled models are accurate for practical purposes.
Improving Injector Efficiencies Using Streamline Simulation: A Case Study in a Giant Middle East Field
Authors: Ghori S. G. , Jilani S. Z. , Al-Huthali A. H. , Krinis D. , Kumar A.
Published: December 2007

Improving and quantifying injector efficiency is a major aspiration in waterflooding operations. Streamline simulation (SL) has a unique advantage over finite-difference simulation because of its ability to quantify the relationships between injectors and producers and to visualize fluid flow patterns.

In this study, streamline simulation was applied to a giant Middle East field to optimize and set injection targets. The objectives were to: (a) formulate an optimization methodology to enhance the overall field injection efficiency and generate injection rates using streamline simulation and (b) constrain the optimization procedure to realistic field conditions to ensure direct field implementation. The ultimate goal is to employ this methodology for routine reservoir management purposes to enhance pressure support and maximize sweep efficiency.

The optimization of injection efficiency is based on increasing the injection rates in efficient injectors and decreasing them by the same amount in inefficient injectors within predefined segments of the field. The boundaries of these segments were established from streamline patterns. It was observed that each segment could be dealt with separately, since each segment was quite independent in terms of injection-production patterns.

With streamline simulation, we were able to generate a workflow that identifies a) distribution of injected water to associated producers, b) water loss to the aquifer, c) percentage of oil produced due to each supporting injector, and d) amount of watercut attributable to each supporting injector. With the proposed methodology the injector efficiencies were increased from 5%-15%, whereas the overall efficiency of each segment was increased by 5%-7%. Considering the size of the giant field, this increase in injector efficiency was significant in the incremental oil recovery. Field examples are presented that show the proposed methodology is beneficial in increasing the overall efficiency, determining monthly injection targets, improving field oil production, and reducing water production.
Drilling Tests of an Active Vibration Damper
Authors: Cobern Martin E. , Perry Carl A. , Barbely Jason A. , Burgess Daniel E. , Wassell Mark E.
Published: December 2007

Drillstring vibration is a serious problem, particularly in deep and hard rock drilling; it can reduce the rate of penetration (ROP), shorten bit life, and damage expensive downhole components. Testing of an active drilling vibration damper (AVD) system at TerraTek Laboratory, under conditions designed to induce vibration, demonstrated that the use of the AVD reduced vibration, maintained more consistent weight-on-bit (WOB) and increased ROP.

The AVD has a structure similar to that of a shock sub with the shock absorber filled with magnetorheological fluid (MRF), rather than hydraulic oil. Under the influence of a magnetic field, MRF instantaneously increases its viscosity. Using a series of coils to induce intense electromagnetic fields across the fluid gap, the damping coefficient can be changed in milliseconds by a factor of 7-10. A linear motion detector provides feedback to control the AVD in response to bit motion.1

In these tests, the AVD was used behind a tricone bit to drill through blocks of hard concrete, each of which had a 12" granite slab mounted within it at a 10° angle. By inducing an asymmetric load on the bit, the interfaces produced severe vibration during drilling the control holes. A total of 28 holes were drilled, including 11 control holes, at varying WOB and rotation rates.

Analysis of the data confirmed the anecdotal observations made during drilling. The vibrations at the bit were reduced significantly; the variation of the measured WOB was significantly curtailed, and the ROP was increased. These tests demonstrated that the AVD is likely to provide significant time and cost savings, particularly in deep wells. These will arise, not only from the increased instantaneous ROP, but also from fewer trips for bit or equipment changes, and lower costs for replacing damaged MWD tools, motors or other expensive components.
Are Swelling-Elastomer Technology, Preperforated Liner; and Intelligent-Well Technology Suitable Alternatives to Conventional Completion Architecture?
Authors: Hertfelder Gary P. , Koerner Kurt , Wilkins Allen , Izquierdo Lilian
Published: December 2007

An independent operator in offshore California has integrated swelling elastomer technology and preperforated liners with triple-zone intelligent well completions for an extended-reach drilling (ERD) campaign in their Rocky Point field. To date, three deployments have been successfully installed in this field, and each has provided successful zonal isolation without conventional cementing and perforating methods.

The Rocky Point reservoir is highly fractured and can rapidly initiate water production, dependent upon both wellbore orientation and fracture network connectivity. Achieving successful zonal isolation is critical to minimize early water production. The arduous task of attaining successful liner cementing practices in high departure and high-angle wells is circumvented by the use of swelling elastomer technology. Additionally, incorporating intelligent well equipment reduces the need for intervention to manage water production because it inherently controls and manages flow rates in each completion interval.

Safety in operational strategies is paramount to this operator. Use of remotely operated downhole valves enhances safety by eliminating the hazards typically associated with conventional well intervention operations, such as tubing-conveyed perforating and coiled-tubing equipment. Additionally, these downhole flow control valves and monitoring equipment minimize the need for platform personnel to expose themselves to high-pressure wellhead components when making adjustments for well optimization.

This paper focuses on the operator's innovative use of advanced completion technologies to lower developmental cost and optimize production rates. Also discussed is the safety provided by the intelligent-well completion systems, which were installed without incident. The three field deployments using swelling elastomer, preperforated liner, and intelligent completion technologies will be discussed along with the initial design, installation objectives, safety attributes, field installation, and performance results. The challenges to deploy these technologies in a highly fractured and highly faulted, complex reservoir will also be presented.
Using GIS as a Data Access and Integration Platform
Authors: Blaha James R.
Published: December 2007

Oil and gas companies around the world are looking for ways to improve efficiency in all aspects of their business. To realize efficiencies, they need to be able to make better decisions faster and cheaper by analyzing all of the relevant data available to them in a systematic fashion. Good decision making starts with quick and easy access to clear and accurate data; no analytical solution, no matter how sophisticated, can compensate for incomplete or inaccurate data. Unfortunately, the data that is needed is very rarely stored in a common format or location and is rarely accessible through integrated, workflow-based, analytical solutions. Instead, users spend a large amount of time tracking down the data they need and loading it into the applications that they use before combining the results to make a final decision.

In the early 1990s, it was believed that monolithic database models and centralized repositories would solve application interoperability concerns. In spite of huge investments and the dedication of leading industry experts, this approach failed. The resulting data models were too complex, and the data conversion costs were too high. Consequently, the petroleum industry data management vision underwent a major transformation during the mid 1990s. A data centric focus was adopted with a resulting shift from the data model to the data itself and the use of meta-data catalogs and middleware to integrate data and applications. To date this approach has yielded some success, but the proprietary nature of the middleware formats and the cost of development of the associated conversion tools makes the resulting solutions expensive and complex to implement and manage.

Over recent years, evolutionary technological advances have presented a more powerful and flexible option for multi-source data access and integration. Data can be managed in its native format and location but is referenced and represented through a de-facto industry standard spatial file structure using the SDE technology from ESRI. This establishes a common data access format that then provides a platform for the integration of information from multiple sources that can be displayed, analyzed, and exported through commercial and customized Web-based or desktop map interfaces.
Water-Based Drilling Fluid for HT/HP Applications
Authors: Tehrani M. A. , Popplestone A. , Guarneri A. , Carminati S.
Published: December 2007

The superior performance of invert emulsion fluids in challenging drilling operations such as HT/HP wells makes them the preferred fluid for such applications. However, there are instances such as drilling in environmentally sensitive areas, or where costs and logistics become prohibitive, where their use is undesirable. In such circumstances, a high-performance water-based drilling fluid is the only option available. A main challenge in developing a water-based fluid for such applications has been to maintain the stability of key fluid properties such as rheology and fluid loss at temperatures in excess of 130°C. Conventional additives, such as biopolymers or synthetic polymers, either become ineffective at such high temperatures or generate too high a rheology when used in quantities needed to curb fluid loss. This paper discusses a novel water-based drilling fluid system in which the synergy of the key fluid components produces a stable rheology and low fluid loss at temperatures approaching 200°C. Furthermore, by balancing the components of the novel system, fluid rheology can be controlled to meet the hydraulics and hole-cleaning demands of the drilling operation.1, 2
Design, Construction, and Optimisation of Big-Bore Gas Wells in a Giant Offshore Field
Authors: Clancey B. M. , Khemakhem A. S. D. , Bene T. F. , Schmidt M. H.
Published: December 2007

An extensive big bore gas well drilling and completions program is in progress to develop the giant North Field, offshore Qatar. Benefits of the big-bore concept, compared to the prior 7-in. monobore design, include reduced development costs by requiring fewer wells, and deferred installation of compression by providing higher flowing wellhead pressures.

This is the widest known application of a big bore design in one single field and involves a large number of wells. Many of these wells are drilled and completed to date and believed to be among the world's most prolific gas producers. These are also the first offshore wells to incorporate big bore well design for large-scale field development and feature industry advances in equipment design and manufacture. An extensive system of detailed design review, equipment performance testing, and quality programs has been implemented to meet challenging project requirements for well reliability.

The wells feature a tapered tubing design known as the "Optimized Big Bore" (OBB). This paper discusses the challenges of planning and executing these OBB wells. It reviews the initial OBB well design, anticipated North Field drilling challenges, critical equipment specifications, and design revisions resulting from optimisation efforts over the past four years.
Achieving Shoe-to-Shoe Drilling Performance in Hole-Opening Application With Rotary-Steerable Systems
Authors: Heisig G. , Hood J. , Okewunmi S. , Robnett E.
Published: December 2007

Detailed analysis of downhole weight-on-bit, torque, bending moment and vibration signals measured between bit and hole opener have provided clear insight into the dynamic response of hole opening BHAs in interbedded formations. Based on transmitted real-time information from an advanced downhole multi-sensor data acquisition and processing system, application-specific drilling procedures and guidelines have been developed to avoid or to identify and overcome critical dynamic situations downhole.

Applying the new procedures, several hole sections in the GOM were drilled for the first time in one run from casing shoe to casing shoe. Here previous attempts had resulted in failures of the drilling equipment or even in twist-offs.

The paper starts with a list of observations made with the downhole multi-sensor tool placed between bit and hole opening device. Log examples with downhole and surface drilling data demonstrate the dynamic response of hole opening BHAs. For the first time, the paper presents downhole measurements showing the changes in weight on bit versus weight on reamer when drilling interbedded formations. Again, log examples are used to document the effect of the drilling procedures that were applied to successfully resolve critical downhole situations. The paper concludes with a summary of the lessons learned in planning and executing hole opening applications with shoe to shoe performance.
Hydraulic Predictions for Polymer-Thickened Foam Flow in Horizontal and Directional Wells
Authors: Chen Z. , Duan M. , Miska S. Z. , Yu M. , Ahmed R. M. , Hallman J.
Published: December 2007

Foam has proven to be effective and economical in underbalanced operations (UBO) and is gaining wider applications in many areas. It provides the desired flexibility in controlling pressure profile and ECD. However, the knowledge of rheology and hydraulics of polymer-thickened foams is still limited. This paper summarizes the significant effects of polymer on foam rheology and presents a hydraulic model that simulates aqueous and polymer-based foam flow in directional and horizontal wellbores.

Experimental studies on the rheology of polymer-enhanced foam were conducted using specially designed a flow-through rotational viscometer and pipe viscometers with different hydroxyethylcellulose (HEC) polymer concentrations. Correlations have been developed for rheological parameters of aqueous and polymer-based drilling foams.

Based on the experimental results of foam rheology and steady-state momentum balance equation, a foam flow hydraulics model was developed to predict pressure profile, ECD, foam velocity and quality along a vertical-inclined-horizontal wellbore. For practical applications, a simulator has been developed and validated by experimental/flowloop data obtained from the Advanced Cuttings Transport Facility of Tulsa University Drilling Research Project (TUDRP). The effects of polymer concentration, back pressure and wellbore trajectory on foam hydraulics were studied extensively using the simulator. Results show significant impact of polymer on foam hydraulics. When 0.5% v/v HEC polymer is added to aqueous foam, Bottom Hole Pressure (BHP) and foam density are significantly increased, while foam quality and velocity are greatly decreased. The polymer effects in vertical wells are more pronounced than in horizontal wells.

Simulation results also indicate that it is possible to use foam to create a pressure profile within the narrow window between continuously changing pore pressure and facture pressure gradients, which is not possible with conventional fluids. Those responsible for hydraulic optimization and well control in MPD/UBO where foam is used will find this paper useful for practical design applications.
Application of Innovative Chemical and Mechanical Processing for Treatment of Difficult Production-Waste Sludge
Authors: Star Jacquelyn F. , Williams Stephen , Sudardjat Isham , Kidder Roger , Gallup Darrell L.
Published: December 2007

East Kalimantan Indonesia has a history of challenges and difficulties in the management and treatment of emulsions, slop oils, slurries and tank bottoms which accumulate in process vessels and tanks. These unresolved production streams, collectively termed "sludge" incorporate strong oil and water emulsions, chemically bound by metal-carboxylate soaps and various mixtures of stabilizing fine sand, scale, and wax.

Previous disposal methods used or considered for use range from very crude methods such as open burning and land-spreading to sophisticated techniques such as slurry fracture injection. However, such options did not provide for oil recovery and posed severe environmental or regulatory problems. The process proven most viable in treatment of sludge employs an aggressive system of heat, customized chemical demulsification, settling, and various means of mechanical/centrifuge separation. In the last several years, more than 500,000 barrels of sludge have been successfully reclaimed at Lawe Lawe and Santan Terminals. Whilst the sludge treatment program overall has been successful, there have also been serious technical challenges and cost-impacts. These difficulties have provided significant lessons learned for both operator and contractor in terms of optimization of key physical, chemical and mechanical separation techniques; as well as for minimizing costs.

A case study of a recent treatment program for over 220,000 barrels of sludge at Santan Terminal will be used to highlight significant implementation and management experience including: Critical equipment selection and design parameters,Chemical treatment requirements,Successful (and unsuccessful) methods for optimization of treatment rate and improving oil recovery,Mechanical challenges for the removal of stabilized fine solids,Key parameters for project tracking, andA realistic assessment of treatment costs.

The results to date illustrate how an effective sludge treatment and reclamation program can provide commercially and environmentally superior results in terms of cost and impacts.
Clustering and Corridoring Project and Challenges
Authors: Elabed Amjad , Ur Rahim Ihtisham
Published: December 2007

By late 90's, Abu Dhabi Company for Onshore Oil Operations (ADCO) started facing increasing surface congestion and related potential operating hazards caused by haphazard laying of new surface assets/facilities in ADCO concession areas due to the implementation of aggressive field development plans. ADCO Management realized very early the need to reduce congestion and reduce the risk to the equipment and personnel while coping with the increased number of surface equipment as business needs expanded. As a result, the Clustering and Corridoring (C&C) Project was launched in 2003 and was divided into three studies phases. Phase I and II studies defined the optimum configuration of the facilities to control congestion and reduce the surface facilities footprint. The studies outcome was the development of four main design concepts:

Exclusion Zones, Well Pairing, Corridors Design, and Radial Corridors Layout.

Phase III studies resulted in the re-defining of Production Pad concept in order to meet the long term field development requirements. To date a total of 97 flowlines have been laid in the corridors in all ADCOs' major fields and a total of 24 wells were clustered since May 2005 in line with the Clustering and Corridoring Project guidelines.
Effect of Length: Diameter Ratio on Collapse Test Results and Frame Design
Authors: Pattillo P. D.
Published: December 2007

The current version of ISO 10400 TR requires a length:diameter ratio of at least seven for sizes larger than 10-3/4. This bound was instituted to account for end effects in a collapse test frame. The requirement currently, however, does not justify the selection of the value of seven, nor does the TR discuss the effect of varying end conditions. This study reviews both experimental and theoretical studies aimed at quantifying the effect of length and end constraints on collapse resistance. The results are intended to (a) justify (or dispute) current ISO 10400 requirements and (b) offer guidelines for adjusting collapse test results when the sample diameter is so large that a length sufficient to satisfy the ISO requirement is impractical.
Gas Blending for Miscible Gasfloods in South Oman
Authors: Deinum G. , Dindoruk B. , O'Dell M.
Published: December 2007

How to ensure that miscibility of oil and gas is achieved in each reservoir is a fundamental issue for miscible gasfloods involving different oil reservoirs with varying fluid properties. This paper reports on all the work done to help decide on how to optimally blend available gas such that miscibility can be achieved in all reservoirs with appropriate focus on the first reservoirs to be flooded. These studies have resulted in an investment decision to undertake a miscible gasflood already in 2005, whereas initial production from four reservoirs had only started in March 2004. Main components of this paper are: (1) Design of experiments for a wide spectrum of fluids (from near-critical systems to black oil systems) using miscible sour gas-blends while minimizing cost and the time spent on the experiments. (2) Acquisition, interpretation of the data (3) Utilization of the data for reservoir engineering/design calculations using a consistent approach for a cluster of sour reservoir fluids, (4) Recommendations based on the experimental data and calibrated simulation models.
Smart Wells Experiences and Best Practices at Haradh Increment-III, Ghawar Field
Authors: Al-Arnaout Ibrahim H. , Al-Zahrani Rashad M. , Jacob Suresh
Published: December 2007

Haradh Increment-III is Saudi Aramco's latest and most advanced developed area in Ghawar field. The area was developed with 32 multilateral wells utilizing advanced drilling technologies to reduce the number of wells and provide maximum reservoir contact at a lower cost per barrel. The complex array of 113 laterals dictates the necessity for individual lateral control for better reservoir management strategy.

Twenty eight smart completions were run in Haradh Increment-III totaling in 87 downhole choke valves installations for flow regulation from different laterals. Throughout the project progress and as more smart completions are installed, Saudi Aramco's experience was ramping up through its learning curve and first-hand knowledge was being gained. The company's experience with smart completion and best practices for ensuring proper functionality of smart completions were being developed with each additional installation.

Detailed project and operational planning is critical to the success of such innovative projects. Operational planning begins before the equipment is manufactured and carries through to equipment assembly, testing and surface tests prior to completions.

The paper presents the experience of Saudi Aramco and the supplier in the installation of 28 intelligent wells, with reliability of 97%, through the adoption of best practices. The development stages of smart completion best practices will be illustrated citing various history cases and addressing important operational concerns.

The learning discussed in this paper will provide an insight into how a large scale application of smart completion technology can be handled in a systematic way to achieve a successful conclusion.
Lessons Learned from Repickling Old/Sour Gas Wells
Authors: Nasr-El-Din H. A. , Garzon F. , Al-Mutairi S. H. , Al-Driweesh S. , Al-Harith A. M.
Published: December 2007

Saudi Arabia has embarked on developing its gas fields. Some of these fields produce sour gases with hydrogen sulfide content that can reach 10 mol% and carbon dioxide of 4-5 mol%. The carbonate formation is very tight and acid fracturing treatments were used to enhance the productivity of these wells. All tubulars were pickled before the acid fracturing treatments. Pickling was needed to remove mill scale (iron oxides) and pipe dope. Invasion of these contaminants into the formation would cause severe formation damage, which might adversely affect the productivity of these wells.

Some of the gas wells have been on production for several years. There was a need to stimulate these wells to perform various workover operations. The question raised was whether there was a need to pickle the tubulars before performing acid treatments to these relatively old wells given the fact that these wells were pickled when the lower zone of the formation was fractured for the first time several years ago. Unlike new wells, the tubulars of old wells are typically covered with various corrosion products, condensate, and pipe dope.

To address the question of pickling of old well tubulars, an acid formulation was designed to remove various contaminants that might present in the wellbore, while maintaining the integrity of the tubulars. The acid treatment was bullheaded in seven wells. Wellhead samples were collected every two minutes during the well flow back and analyzed for key elements.

Similar to new tubulars, field data indicated that there is an absolute need to pickle old tubulars. High concentrations of total iron were detected in the well flow back samples. Manganese concentration was relatively low, indicating the acid pickling treatment did not affect the integrity of the low-carbon steel tubing. This paper describes in detail the laboratory work, treatment design, and field application. It will give conclusive evidence on the importance of pickling old tubulars and highlight the need for such treatments.
New Cement Formulation that Solves Gas Migration Problems in Iranian South Pars Field Condition
Authors: Pour M. Mohammadi , Moghadasi J.
Published: December 2007

Gas migration through cement columns has been a problem of the oil and gas industry for many years. The most problematic areas in Iranian South Pars Field operations for gas migration are in gas wells; which causes failure of about 30 % of the primary cement jobs. Gas migration in these gas wells occurs when drilling through the Kangan and Dalan formations. To control gas influx, cement densities required to successfully cement this zone could be as high as 120 pcf. Specially designed cements were used to "zone isolate" the high pressure coming from the formation. High density/low fluid loss cements were used in the past with limited success. The objective of this study was to develop an effective cement formulation to control deep gas migration during primary cementing. To measure major slurry properties lab equipments were utilized for this study. A static gel strength analyzer (SGSA) is used to determine the static gel strength of formulated well cements to confirm the data from previous experiments on the slurry (rheology, filtration, and free water). Results from the SGSA were utilized to reduce the gas migration problem. This study also discusses the individual components necessary for gas-leak elimination. In addition, clearly addresses the gas migration problems related to cementing operations.
Support Vector Machines Framework for Predicting the PVT Properties of Crude-Oil Systems
Authors: El-Sebakhy E. , Sheltami T. , Al-Bokhitan S. , Shaaban Y. , Raharja I. , Khaeruzzaman Y.
Published: December 2007

PVT properties are very important in the reservoir engineering computations. There are many empirical approaches for predicting various PVT properties using regression models. Last decade, researchers utilized neural networks to develop more accurate PVT correlations. These achievements of neural networks open the door to both machine learning and data mining techniques to play a major role in both oil and gas industry. Unfortunately, the developed neural networks correlations have some limitations as they were originally developed for certain ranges of reservoir fluid characteristics and geographical area with similar fluid compositions. Accuracy of such correlations is often limited and global correlations are usually less accurate compared to local correlations. Recently, support vector machines have been proposed as a new intelligence framework for both prediction and classification based on both structure risk minimization criterion and soft margin hyperplane. This new framework dealt with kernel neuron functions instead of sigmoid-like ones, which allows projection to higher planes and solves more complex nonlinear problems. It has featured in a wide range of medical and business journals, often with promising results. The objective of this research is to assess the benefit of support vector machines as decision making tools in the field of oil and gas industry.

To demonstrate the usefulness of the support vector machines technique in petroleum engineering area, we describe both the steps and the use of support vector machine modeling approach for predicting the PVT properties of crude oil systems. A comparative study will be carried out to compare their performance with the performance of the neural networks, nonlinear regression, and the empirical correlations algorithms. A preliminary results show that the performance of support vector machines will be accurate, reliable, and outperform most of the existing approaches. Future work can be achieved by using this new framework as a modeling approach for solving oil and gas industry problems, such as, permeability and porosity prediction, identify liquid-holdup flow regimes, and other reservoir characterization.
Overcoming the Loss of a Primary Barrier in an HP/HT Well—Investigation and Solution
Authors: Humphreys Alan , Ross Robert
Published: December 2007

The failure of a primary barrier on a completed HPHT well in the West Franklin field in the UKCS in 2005 resulted in a significant pressure increase in the production annulus requiring a complex well kill operation to resolve. Following this incident an investigation programme was undertaken to determine the root cause of the failure and, thereafter, to develop a solution. The failure investigation looked at all aspects of the well design and operations and found no clear cause. A ‘failure test’ was then carried out which recreated the exact downhole conditions on surface. This test demonstrated that very small irregularities in the internal casing profile would cause packer to casing seal failure under severe bottom hole conditions. A programme was then undertaken to develop a packer seal system, suited to the severe well environment, that could withstand a specified degree of casing irregularity. A rigourous qualification programme was also developed to verify the new systems capability in irregular casing.

The programe was completely successful and new packer seal systems have been qualified to these enhanced standards and deployed in the field.
A Case Study of the World's First Maximum-Reservoir-Contact Well With Intelligent Well Systems and MultiPhase Flow Monitoring
Authors: Al-Bani Fahad , Al-Sarrani Hassan , Arnaout Ibrahim , Anderson Adam , Aubed Yaser , Johansen E. S.
Published: December 2007

In today's drive to improve well production, more innovative methods are continually being implmented to enhance well productivity and reservoir management. Remote monitoring and interactive control are two such methods that are more frequently employed to derive more value from wells. In Saudi Arabia, the world's first maximum reservoir contact (MRC) well, using Intelligent Well Systems and fiber-optic monitoring to maximize production performance was implemented.

This paper discusses the implementation of remote monitoring and interactive control systems on Well-194, which was drilled as a tri-lateral MRC well with 4.2 km (2.61 mi) of total reservoir contact. The Intelligent Well System utilized feed-through production packers to isolate each of three laterals in the motherbore. Three remotely operated downhole chokes were installed to independently control flow from each lateral for the purpose of optimizing overall well production. This control extends the production plateau while maximizing reservoir drainage. The fiber-optic monitoring system enables remote monitoring of key production parameters, including pressure, temperature, total flow rate and water cut from each of the laterals, used to determine optimum downhole choke settings. Finally, the well was implemented as "ESP Ready" with 7" tubing and a Deep-Set SCSSV to enable subsequent installation of a thru-tubing ESP to further improve production.

Ultimately, this configuration resulted in a well capable of producing at a very high rate with low drawdown for an extended period of time. This strategy will result in a long-term sustained rate while optimizing the reservoir drainage process. This paper will review the lessons learned and key issues around implementing this type of "Next Generation" well completion system.
Anionic Surfactant Gel Treatment Fluid
Authors: Welton Thomas D. , Bryant Jason , Funkhouser Gary P.
Published: December 2007

Typical viscoelastic surfactant gels used for gravel packing and hydraulic fracturing have relied upon cationic, amphoteric, or zwitterionic surfactants as their primary gelling agent, complicating the stimulation of some wells due to wettability or formation fluid compatibility issues. This paper describes an anionic viscoelastic surfactant developed for fracturing and gravel packing applications. The performance of the gel as a function of temperature, salt type and concentration, and cosurfactant will be presented along with the chemical structure/activity relationship. Rheological measurements demonstrate that fluids made with the new anionic surfactant have effective performance over a range of conditions encountered in treating wells.
Deflation AMG Solvers for Highly Ill-Conditioned Reservoir Simulation Problems
Authors: Klie Hector , Wheeler Mary F. , Clees Tanja , Stüben Klaus
Published: December 2007

In recent years, deflation methods have received increasingly particular attention as a means to improving the convergence of linear iterative solvers. This is due to the fact that deflation operators provide a way to remove the negative effect that extreme (usually small) eigenvalues have on the convergence of Krylov iterative methods for solving general symmetric and non-symmetric systems.

In this work, we use deflation methods to extend the capabilities of algebraic multigrid (AMG) for handling highly non-symmetric and indefinite problems, such as those arising in fully implicit formulations of multiphase flow in porous media. The idea is to ensure that components of the solution that remain unresolved by AMG (due to the coupling of roughness and indefiniteness introduced by different block coefficients) are removed from the problem. This translates to a constraint to the AMG iteration matrix spectrum within the unit circle to achieve convergence. This approach interweaves AMG (V, W or V-W) cycles with deflation steps that are computable either from the underlying Krylov basis produced by the GMRES accelerator (Krylov-based deflation) or from the reservoir decomposition given by high property contrasts (domain-based deflation). This work represents an efficient extension to the Generalized Global Basis (GGB) method that was recently proposed for the solution of the elastic wave equation with geometric multigrid and an out-of-core computation of eigenvalues.

Hence, the present approach offers the possibility of applying AMG to more general large-scale reservoir settings without further modifications to the AMG implementation or algebraic manipulation of the linear system (as suggested by two-stage preconditioning methods). Promising results are supported by a suite of numerical experiments with extreme permeability contrasts.
Algebraic Multigrid Methods (AMG) for the Efficient Solution of Fully Implicit Formulations in Reservoir Simulation
Authors: Stüben Klaus , Clees Tanja , Klie Hector , Lu Bo , Wheeler Mary F.
Published: December 2007

A primary challenge for a new generation of reservoir simulators is the accurate description of multiphase flow in highly heterogeneous media and very complex geometries. However, many initiatives in this direction have encountered difficulties in that current solver technology is still insufficient to account for the increasing complexity of coupled linear systems arising in fully implicit formulations. In this respect, a few works have made particular progress in partially exploiting the physics of the problem in the form of two-stage preconditioners.

Two-stage preconditioners are based on the idea that coupled system solutions are mainly determined by the solution of their elliptic components (i.e., pressure). Thus, the procedure consists of extracting and accurately solving pressure subsystems. Residuals associated with this solution are corrected with an additional preconditioning step that recovers part of the global information contained in the original system.

Optimized and highly complex hierarchical methods such as algebraic multigrid (AMG) offer an efficient alternative for solving linear systems that show a "discretely elliptic" nature. When applicable, the major advantage of AMG is its numerical scalability; that is, the numerical work required to solve a given type of matrix problem grows only linearly with the number of variables. Consequently, interest in incorporating AMG methods as basic linear solvers in industrial oil reservoir simulation codes has been steadily increasing for the solution of pressure blocks.

Generally, however, the preconditioner influences the properties of the pressure block to some extent by performing certain algebraic manipulations. Often, the modified pressure blocks are "less favorable" for an efficient treatment by AMG. In this work, we discuss strategies for solving the fully implicit systems that preserve (or generate) the desired ellipticity property required by AMG methods. Additionally, we introduce an iterative coupling scheme as an alternative to fully implicit formulations that is faster and also amenable for AMG implementations. Hence, we demonstrate that our AMG implementation can be applied to efficiently deal with the mixed elliptic-hyperbolic character of these problems. Numerical experiments reveal that the proposed methodology is promising for solving large-scale, complex reservoir problems.
Efficient History Matching and Production Optimization With the Augmented Lagrangian Method
Authors: Doublet D. C. , Aanonsen S. I. , Tai X. -C.
Published: December 2007

A new method for reservoir history matching and dynamic optimization of water flooding with smart wells is presented. For the dynamic optimization of water flooding case, we solve a constrained optimization problem where the net present value is maximized and the reservoir flow equations are considered as constraints. Similarly for the history matching, we recover the permeability field from measurements of pressures and saturations. In both cases the problem is formulated as finding a saddle point of the associated augmented Lagrangian functional. We compare the method with a more traditional optimal control method, based on solving the adjoint system of equations. In the examples tested the new method obtains approximately the same results using the same or less computational effort compared to the adjoint method. An advantage of the new method is that we do not solve the flow equations exactly at each iteration. As the optimization proceeds, the flow equations will be fulfilled at convergence. Thus, each iteration of the new minimization algorithm is cheaper than for the adjoint method.