bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Coiled Tubing Equipment to Run Complex Jointed Tubing Velocity Strings
Authors: Rignol J. , Krepa J. -M. , Hogan E. , den Besten H.
Published: December 2007

The cost of remedial work on marginal gas wells suffering from water unloading problems can be prohibitive, especially in an offshore environment. The expected financial return often does not justify the rig costs associated with pulling and running a new completion, while the formation damage caused by many well-killing methods can reduce the production potential of already marginal wells.

A Coiled Tubing velocity string can often prove a quick and cost-effective method of assisting in water unloading. The ability to work in live well conditions avoids damaging the formation, making it an ideal solution in many cases. However, the limited lifespan of carbon steel strings in corrosive environments calls for a different solution. The next option is often to run and hang off a chrome tubing string with a snubbing unit, which makes running corrosion-resistant tubing in live well conditions possible. However, the higher costs and increased time associated with a snubbing unit reduce its attractiveness.

The unconventional operational procedure of running corrosion-resistant jointed tubing with Coiled Tubing equipment has been used on few occasions to combine the benefits of Coiled Tubing and snubbing interventions. Although generally restricted to relatively short tailpipes, this method has on occasion been extended to running full velocity strings. The limited tensile load capacity of the externally flush threads has limited the length of the string in some cases.

A solution to this problem where a complex string is run in two independent sections has been applied in the field to increase the total velocity string length to 4115m.

The paper discusses the design and execution of the operation where Coiled Tubing and jointed tubing were used as a complex velocity string in order to restore production on a gas well, while retaining the full functionality of the downhole safety valve. Particular attention will be paid to the design of the string, which had to be tailored to remain within the operating envelope of the externally flush thread.
External corrosion of pipelines: What risk?
Authors: Roche M.
Published: December 2007

The paper gives a contribution to the problematic of external corrosion of pipelines. The performance of plant and field joint coatings is detailed and interference between coatings performance and cathodic protection efficiency is evaluated.

Recent failures on a buried onshore 18" refinery pipeline coated with FBE and a buried onshore 18" oil pipeline coated with 3 layer low-density polyethylene and heat-shrinkable sleeves applied over a liquid epoxy primer are presented and commented. The so-called "cathodic protection shielding ef-fect" prevents cathodic protection current to flow to areas submitted to corrosion risk under disbonded coatings.

The most critical zone for offshore pipelines is the transi-tion area between riser thick coatings and atmospheric paint system where accelerated corrosion may occur.
Data on Demand: The Emerging Global Business Case
Authors: Kozman J. B.
Published: December 2007

Information management project implementations remain some of the most challenging in the petroleum technology sector. While a growing body of metrics and measurements demonstrates the impact of data and information management implementations on the profitability of oil and gas operations, many organizations are still unable to justify the benefits with a valid business case as prescribed by standard project management methodology.
En Route to the e-Field: Effective Decision Making Assisted by E&P Web Portal Solutions
Authors: Giménez L.
Published: December 2007

Currently, nearly all oil and gas upstream organizations utilize some sort of digital workspace tools to access their petrotechnical data. This paper provides an insight into the role of the digital workspace in improving operations based on data browsing and access in real- or near-real time by utilizing Web portal tools that ▪Reduce exploration and development cycle times▪Enhance reservoir recovery▪Optimize production▪Significantly decrease personnel needed in high-risk, high-cost areas.

These improvements are made possible by leveraging network connectivity (Intranet, Internet) and intelligent systems. By bringing E&P-qualified data and information to the user's petrotechnical desktop, productivity increases, collaboration is promoted, and knowledge is shared among members of the communities within the organization.

Field data is either captured manually or digitally streamed from automated devices that take readings directly from wells and/or production facilities. High-frequency data historians are linked to corporate master data stores. Users access the information from these disparate repositories through a common standard single-point Web interface that is fully customizable. This information is extracted and can be displayed in the form of location maps, bubble maps or pie charts, tables, reports, and charts. Users also have access to systems for faster effective decision making that warn them based on thresholds, key performance indicators (KPIs), and smart alarms. These systems integrate finance and petrotechnical information, including lifting cost per asset team, production sales, field/facility/well production volume, highlights on recent well tests, well test and/or production (injection) variations, well status (downtime) alerts, well trend analysis, comparison detail on distinct operations types, casing running time, wellbore schematics, daily drilling reports, completion and workover information, health, safety, and environmental information, etc. By connecting people to data and information, upstream organizations ensure access to exactly what geoscientists and engineers need to do their jobs in a better and more efficient way, improving the quality and speed of the decision taking.

Three specific Middle Eastern case implementations are herein detailed as examples of how Web portal data access solutions provide optimization and automation of E&P workflows.
Stress Corrosion Cracking of Corrosion Resistant Alloys in Brine Packer Fluids
Authors: Craig B. D. , Webre C. M.
Published: December 2007

There have been several recent failures of corrosion resistant alloy (CRA) tubing strings in brine packer fluids as a result of stress corrosion cracking (SCC). These failures have been unexpected based onearly studies that only examined the various brine fluids and common CRAs without concern for the impact of inhibitors added to the brine and the charging of the brine with acid gases from leaks in the tubing or packer connections. This paper presents laboratory work that demonstrates 13Cr and 22Cr alloys are very susceptible to SCC in brines charged with CO2 and H2S even at moderate temperatures but that the high nickel alloys, such as Alloy 825 are much more resistant.
Stimulation of High-Temperature Sandstone Formations From West Africa With Chelating Agent-Based Fluids
Authors: Ali S. , Ermel E. , Clarke J. , Fuller M. J. , Xiao Z. , Malone B.
Published: December 2007

Fluids based on chelating agents have been developed for matrix stimulation of high-temperature sandstone formations. These fluids dissolve sizeable amounts of calcite and clays and maintain high levels of dissolved metal in solution over time with minimal precipitation. A series of field samples from high-temperature (149°C) sandstone reservoirs in a West African formation bear carbonate concentrations ranging from 2 to 37% (w/w). The effects of matrix treatment using a chelating agent-based system on these field samples were studied using coreflood and slurry reactor experiments.

Linear coreflood test data show dramatic increases in the formation permeability after treatment with the chelating agent-based fluid. The improvement in permeability is ascribed to the removal of carbonate minerals and soluble clays, without secondary metal-precipitation. Slurry reactor tests elucidated the kinetics of mineral dissolution in mechanically ground field samples. Treatment with acidic chelant fluids generated high levels of dissolved calcium, silicon, and aluminum that remained in solution over time. For comparison, conventional mineral-acid treatment of the field samples generated high levels of metals in solution that declined over the same period of time, indicative of secondary precipitation. The effectiveness of the chelant fluid for stimulation of this high-temperature formation was confirmed through increased formation permeability and high levels of dissolved minerals.
A Pore Network Modeling Approach to Predict Petrophysical Properties of Diatomaceous Reservoir Rock
Authors: Jia L. , Ross C. M. , Kovscek A. R.
Published: December 2007

A novel three-dimensional pore network model of two-phase flow was developed to compute permeability, relative permeability, and capillary pressure curves from pore-type size and shape data information measured via high resolution image analysis of rock samples. The diatomite model is constructed using pore-type proportions obtained from image analysis of epoxy-impregnated polished samples and capillary pressure curves for diatomite cores. Multiple pore types are measured and each pore type has a unique pore size and throat size distribution that is incorporated in the model. Network results present good matches for relative permeability and capillary pressure when compared to experimental measurements. The pore network model is applicable to both drainage and imbibition within diatomaceous reservoir rock. Correlation of network model results to well log data is discussed, thereby interpolating limited experimental results across the entire reservoir column. Importantly, our method has potential to predict petro-physical properties for reservoir rocks with either limited core material or for which conventional experimental measurements are difficult, unsuitable, or expensive.
Exposing Accidents: Moving Safety Focus from Likelihood to Exposure
Authors: Spigener J.
Published: December 2007

This paper discusses how changing the organizations focus from preventing accidents to exposure reduction is a critically necessary step to achieving a zero injury culture. This focus adjustment allows a company to no longer try to define which actions and judgments will be at the root of the next injury or event. The initial discussion begins with an examination of the problem with an injury-focused safety program as well as the working interface between the worker and the equipment. The difference between making decisions on actions based on whether I think there is a likelihood of an injury and whether exposure is changing regardless of the possible outcome will be explained. This seemingly small obtuse point will be illustrated with the use of several everyday examples. We will examine five areas in which a shift to exposure focus can occur. Lastly, we will leave you with some suggestions about going forward in your safety focus planning.
A Novel Approach to Eliminating Sulfur Deposition in Liquid Redox Hydrogen Sulfide Removal Systems
Authors: Roberts J. A. , Roberts R. S.
Published: December 2007

Hydrogen sulfide-rich natural gas is a common by-product of thermally enhanced oil production in California's San Joaquin Valley. Regulatory emission limits necessitate the removal of sulfur compounds prior to incineration of the natural gas in steam generation units. Aera Energy LLC utilizes the SulFerox® process for sulfur removal at several operating locations. Sulfur deposition is a common problem within the piping and vessels throughout SulFerox systems.

The Aera Moco SulFerox facility produces over 1.5 long tons of sulfur per day. Plant shutdowns were typically required every six weeks to remove solid sulfur accumulation within the gas sparger vessel and skid piping. An engineering study was initiated to determine how to best reduce the operational disruptions caused by these frequent cleanings. Following the investigation of several alternatives, a daily online cleaning method involving the redesign of the sparger gas injection piping was installed. This redesign involved retrofitting the sparger vessel with an improved lateral design that resulted in increased gas velocity as well as improved gas distribution. In addition, the laterals were configured so that each one could be individually taken offline and cleaned with a "blast" of natural gas while the sparger vessel remained in service. This method was chosen over several alternatives due to its relatively low installation cost, low operating cost, high reliability, and elimination of personnel exposure hazards. Since implementing the online cleaning system in September 2003, the sparger vessel remained in service for one year before it was taken offline for cleaning and inspection.

This paper discusses the online cleaning system design as well as several alternatives that were investigated. The successful results to date are reviewed along with potential future system enhancements.
Combining Geostatistics with Dynamic Modeling to Improve Reservoir Management Strategies: A Case Study from the Balingian Province
Authors: Finol J. , Dronamraju S. , Zakaria A. A. , Koraini A. M.
Published: December 2007

This paper presents an application of geostatistic in the context of a full field review study for D18 field. A two-stage stochastic modeling approach is applied to distribute the reservoir heterogeneities resulting from different rock types and the inherent spatial variability of the petrophysical rock properties. Firstly, facies distribution is simulated while preserving the main fault features. Secondly, porosity and permeability images are simulated on the basis of facies distribution, providing small-scale variability of these two properties. The fine-scale stochastic grids are upscaled to coarser simulation grids for dynamic reservoir modelling and initialized to static equilibrium condition. Production history match is used as the ranking criterion for selecting the reservoir model to be employed for production forecasting.
A Method for Pattern Recognition of WOR Plots in Waterflood Management
Authors: Yang Z. , Ershaghi I.
Published: December 2007

Pressure maintenance by waterflooding is a prominent recovery process in many of California oilfields. Majority of these turbidite sandstone reservoirs contain highly heterogeneous permeability profiles affected by alternation of sand shale sequences and the clay content. A typical signature of such heterogeneous profiles is often the existence of a high permeability streak serving as a "thief zone". Mechanical or chemical blocking of such layers on the injection or production side has been an objective of water flood management.

This paper presents a novel method for using a series of customized type curves to scrutinize the WOR characteristics plots of producing wells in stratified reservoirs. From a library of systematically generated performance plots for several combination of rock and fluid properties, and various architectural position of the high permeability zone, the actual data for a given well or a group of wells can be matched against various patterns to identify the degree of heterogeneity and the potential existence of a high permeability streak. With such a pattern recognition tool, opportunities to enhance the performance of individual wells or group of wells can be ascertained. Additionally, the impact of permeability modification by mechanical or deep chemical zonal isolation has also been studied. In brief, we have generated yardsticks by which the effectiveness of wellbore isolation or in-depth plugging of high permeability streak can be examined.
Applications of Pulsed Neutron Capture Logs in Reservoir Management
Authors: Morris F. , Morris C. , Quinlan T.
Published: December 2007

Pulsed neutron capture (PNC) tools are considered a primary evaluation means in reservoir monitoring and surveillance. Systematic time-lapse PNC logging gives a detailed and dynamic picture of the reservoir saturation response to production and injection operations. The neutron capture cross section measurements offer the essential means to monitor hydrocarbon saturation, water breakthrough, and fluid contact changes in a timely manner.

The recent introduction of a new generation of pulsed neutron capture logging tools has lead to a reappraisal of the design of reservoir monitoring logging programs. Efficient reservoir management requires that the latest PNC tool technology be comparable with the older measurement results to provide continuity, precision, and accuracy in the monitoring program. A new sigma processing technique was developed for the dual-burst pulsed neutron capture measurements to accomplish this objective. This technique maintains the resolution and repeatability of the new-generation tools but provides results needed for reconciliation with the older generation tools used for more than 20 years in reservoir monitoring.

The sigma processing technique is described relative to the old and new generation tools, which utilize radically different approaches. Diffusion, borehole, and lithology effects must be considered when transforming observed quantities such as decay times or near-to-far ratios to actual physical quantities. General considerations of repeatability and accuracy are discussed which apply to PNC logs and their use in both stand-alone and time-lapse techniques.

More than 30 cases have been evaluated with the new processing technique. Examples are presented that show reservoir monitoring results obtained in a wide variety of formation lithologies, formation fluids, and borehole environments to illustrate the robustness of the technique. These cases include detailed analytic studies between the PNC tools. The results indicate that the new sigma processing can provide direct time-lapse reservoir monitoring continuity and yield accurate reservoir saturation analysis.
Direct Monitoring of the Performance of Scale Control Programs Across the Produced Water Life Cycle Via Suspended Solids Analysis
Authors: Jordan M. M. , Buckman J. , Johnston C. J.
Published: December 2007

Effective scale control in production of hydrocarbon deposits is in many fields essential to the economic and safe production of hydrocarbon and associated fluids. Chemical inhibitors of inorganic scale (carbonate and sulphate) have long been applied to subsurface (continual injection or squeeze) to flow lines/process equipment along with the growing area of produced water reinjection. The following paper will outline a method of improved performance monitoring of such chemical treatments. The measurement of suspended solids is a common practice to determine injection water quality but the measurement of the type, amount, texture and composition of solids within produced fluids via environmental scanning electron microscopy (ESEM) combined with energy dispersive analysis (EDX) has not until now been used as a routine method to monitor the effective scale control programs applied downhole, topside and for produced water reinjection. The collection/filtration of small quantizes of produced water that are subsequently analyzed for the texture and composition of sulphate/carbonate solids has been used in a number of fields within the North Sea and Gulf of Mexico as a direct method of scale inhibitor performance. This novel method of measuring chemical performance that does not rely on chemical or brine analysis and allows drilling related solids to be differentiated from scale formed within produced brine. The paper will present results from 4 fields to illustrate the value this method of monitoring was able to bring the field operators to optimize scale squeeze treatments and topside treatment rates.
Low Salinity Oil Recovery: An Exciting New EOR Opportunity for Alaska's North Slope
Authors: McGuire P. L. , Chatham J. R. , Paskvan F. K. , Sommer D. M , Carini F. H.
Published: December 2007

Laboratory studies conducted over a period of many years have indicated that oil recovery could be improved by injecting lower salinity water (less than about 5,000 ppm). Although the recovery mechanisms are still uncertain, they appear to be similar to those found in alkaline flooding. Recent successful field trials have led to serious evaluation of field-scale implementation of low salinity EOR.

Four sets of single well chemical tracer tests (SWCTT) performed in Alaska confirmed that the favorable laboratory results could be replicated in the field. The SWCTT results (two in the Ivishak sandstone, one each in the Kuparuk and Kekiktuk sandstones) showed that waterflood residual oil saturation (Sorw) was substantially reduced by low salinity water injection. The low salinity EOR (LoSal) benefits ranged from 6 to 12% OOIP, resulting in an increase in waterflood recovery of 8 to 19%. Based on these encouraging results, low salinity oil recovery is being actively evaluated for North Slope reservoirs.
A New Method to Evaluate Cement Systems Design Requirements for Cyclic Steam Wells
Authors: Myers S. , El Shaari N. , Dillenbeck L.
Published: December 2007

Evaluating a cement system for zonal isolation and its ability to support the casing have always, among other parameters, used compressive strength as an important set cement slurry requirement. Recent studies have concluded that compressive strength is not the most important characteristic of the cement to provide zonal isolation and casing support. Elasticity and tensile strength of the cement system is more important for casing support and zonal isolation. In Kern county California, cyclic steam wells are a common completion method for heavy oil recovery. These wells may have temperature variations between production and steam injection cycles of up to 300°F. These extreme wellbore temperature swings create a large amount of induced stress on the cement sheath. Currently, the industry approach is to develop the highest compressive strength cement system possible to maximize cement bonding. However, advanced modeling now available indicates that such systems might not be optimized for such applications. A lightweight cement system has been developed and laboratory tested utilizing fit-for-purpose additives to give the set cement enhanced elastic and tensile properties. This paper will discuss the design and development, along with the potential application of an enhanced set-cement mechanical property system. The results of a Cement Stress Model, and the impact on cementing cyclic steam wells will also be presented.
Performance of Downhole Separation Technology and its Relationship to Geologic Conditions
Authors: Veil J. A. , Quinn J. J.
Published: December 2007

Management of produced water presents challenges and costs to operators. If the entire process of lifting, treating, and reinjecting can be avoided, costs are likely to be reduced. Oil and gas industry engineers have developed various technologies that separate oil from water or gas from water inside wells. These devices are known as downhole oil/water separators (DOWS, or according to some, DHOWS) and downhole gas/water separators (DGWS). This paper summarizes a recent report by Argonne National Laboratory that provides data on 59 DOWS trials and 62 DGWS trials from around the world. The report focused on the performance success of each trial and the geological conditions of the producing and injection formations. The goal of the study was to identify the types of geological formations that would present the best chance of success for future DOWS or DGWS trials. Upon reviewing these DOWS and DGWS installations, we concluded that it was not possible to predict the success of an installation solely on the basis of the geology of the production formation or injection formation.
Evaluation and Optimization of Solids-Control Equipment Systems Reduce Waste Volumes, Improve Safety, and Lower Costs
Authors: Rengifo R. , Browning K. , Carruyo F. , Bernal G. , Figueroa V. , Medina J.
Published: December 2007

Proposal

In their efforts to optimize solids control systems, companies in this region have implemented improvements in both the equipment design and operational performance, in order to reduce fluid maintenance costs and decrease the volumes of fluid lost on the cuttings. These improvements helped to optimize the operation and the number of units used during the operation, while maintaining excellent mechanical removal efficiency in the solids control units.

In 2001, after completing a comprehensive evaluation of the "dryer centrifuge" system used in Venezuela by PDVSA-Oriente, a major drilling fluids company proposed that PDVSA test a new array in the solids control equipment (SCE) system. The first phase addressed the incorporation of a flow distributor at the end of the return line and the redistribution of the flow line shakers in parallel form. The results obtained in this first phase made it possible to propose new recommendations implemented in a second phase of the optimization study, which was based on reduction of the number of units (de-incorporation of the screw conveyor and the dryer screen) and optimization in the design of the screen mesh.

This paper presents the results obtained by applying a new focus for evaluation and optimization of solids control services on drilling rigs. The optimization plan was carried out on nine rigs. Costs associated with solids control service were reduced because fewer units were needed, less fluid volume required processing, the screen design allowed for a more efficient consumption rate, and the volume of fluids to be disposed of environmentally were monitored and managed better. Moreover, the technical competency of the field personnel was improved and, even though fewer units were used, a good balance was maintained between efficient service and the removal of fluid from the drill cuttings.
An Effective Solution To Repair Severely Corroded Casing Strings: Applications in the Oriente Basin of Ecuador
Authors: Simbala V. , Palomeque M. , Evers R. , Ordonez E.
Published: December 2007

In the Oriente basin of Ecuador several operators, including the National Petroleum operator, are producing oil at approximately 455,000 B/D and having high numbers of workovers. Many wells have been closed because they were considered uneconomic, and studies have been carried out to re-open them and increase the production.

Some operators have big problems because of aggressive corrosion in the old strings. In many wells the corrosion is so great that a part of the casing literally disappears. Splits and cracks are very common in old strings. Under these conditions, the life of the well is limited to the life of the casing if a good solution is not found.

To solve these problems, we demonstrated a use of special fibers technology that is outside its original design purpose. From the economical side to close a well means to lose the investment made in the well and lose the oil production. For this reason, finding a good technical solution that allows the wells to be reopened adds value to an existing asset and contributes to ultimate recovery.

In the past conventional cement slurries were used to address the problem with poor results; the cement could not support the pressure test.
Evaluation of Static Friction in Coiled Tubing HPHT Operations Using Real-Time Data
Authors: Pittman I. , Christie M. P.
Published: December 2007

Coiled tubing (CT) is being pushed to the limits of its capability by the more complex and challenging nature of wells currently being drilled. Either the yield limits are being approached because of the extremely deep high pressure, high temperature (HPHT) wells, even with the use of 100,000-psi strength CT, or the reach capability is being surpassed by the long step out of horizontal wells. To accurately predict the results of such an intervention, the planning phase must include detailed modeling combined with previous experience.

This paper will describe the theoretical effect that static friction would have on CT well interventions and compare this with the actual values found through the analysis of data recorded real time on the same wells. Static friction will be quantified in a number of HPHT wells and the resulting effect on the force required to pull out of hole will be presented. Testing performed to evaluate the static friction through the stripper will also be presented. These values will be used to help ensure the CT well bore friction is accurately quantified.
High Pressure High Temperature Coiled Tubing Intervention Operations in the North Sea Within the Past Two Years
Authors: Turner A. , Murdoch B.
Published: December 2007

High Pressure High Temperature (HPHT) fields in the North Sea continue to both push, and ultimately extend, the boundaries of what can be safely and successfully achieved through intervention with coiled tubing (CT). Within the last six years successful CT deployed perforating operations have become relatively common. However, as more and more HPHT fields consider intervention operations, existing technologies are subsequently examined and re-examined to suit the particular well criteria and also the actual operating environment of the particular offshore installation.

This paper begins by discussing the types of equipment that are required for HPHT CT intervention. It then presents a number of recent case histories concerning CT interventions on HPHT fields. Three of these case histories involve different underbalance perforating operations. Case histories concerning cementing operations through CT are also discussed. The paper outlines the specific types of downhole equipment that are needed for these operations. This includes application of new equipment designs and novel solutions to both surface and downhole constraints.

Lessons learned from each of the case histories will be presented together with an overview of the requirement that HPHT fields and the related CT intervention technologies are moving towards. Conclusions will be drawn from these different case histories and a discussion presented on the potential extension for CT intervention in HPHT environments.
Simulation of Inflow whilst Underbalanced Drilling (UBD) with Automatic Identification of Formation Parameters and Assessment of Uncertainty
Authors: Friedel T. , Mtchedlishvili G. , Voigt H.-D. , Häfner F.
Published: December 2007

Underbalanced drilling (UBD) is defined as a drilling operation where the pressure of the circulating drilling fluid is lower than the pore pressure of the target formation of interest. The most widely recognised benefit of UBD is the reduction of formation damage by minimising the drilling fluid leakoff and fines migration into the formation. It also facilitates the possibility for reservoir characterisation during drilling. The purpose of this paper is to present (i) how to use the inflow data for the evaluation of formation properties and (ii) how to cope with the uncertainty of the results.

An in-house multiphase reservoir simulator is used for the simulation of the formation reservoir fluid flow during UBD. The model incorporates discrete consideration of the well with appropriate, time varying UBD boundary conditions. Capillary forces, which facilitate countercurrent imbibition of the drilling mud into the formation, are taken into account.

The production rates during UBD depend on the formation properties and the drilling conditions. The inflow information is analogue to transient test data and can be used for the estimation of the reservoir model parameters. With the advancing of the drilling process, the amount of available inflow data increases and allows for a sequential history match procedure. Based on a statistical analysis of the inverse problem we identify the optimal level of parameterisation as quality and quantity of the measured data justifies.

Technical contributions of this paper include (i) the usage of a reservoir simulator to derive the inflow of fluids in heterogeneous reservoirs and (ii) its coupling with gradient- based optimisation techniques for determination of certain reservoir parameters. The "simulation while drilling" approach proposed is fully automated and can set-up on a known or totally unknown reservoir model, introducing an iterative and automatic updating process of the reservoir model.
Development of a Thermodynamic Model and Reservoir Simulator for the CH4, CO2, and CH4-CO2 Gas Hydrate System
Authors: Zhu T. , McGrail B. P. , Kulkarni A. S. , White M. D. , Phale H. , Ogbe D.
Published: December 2007

An equation of state (EOS) software module was developed for CH4, CO2, and CH4-CO2 mixed hydrates by using VanderWall-Platteeuw model. The model is based on classical thermodynamics and is used to predict the thermodynamic behavior of gas hydrates including pressure and temperature at which gas hydrates form. A numerical scheme was developed for solving Lw-V-H and I-V-H equilibrium conditions for bulk hydrate formation from pure water and gas. The model was further extended to determine hydrate equilibrium conditions in the presence of salt. The results calculated from the model were in close agreement with the experimental data reported in literature. One of the contributions of this work is that the proposed model can predict hydrate dissociation pressures at temperatures above 285 K more accurately than any of the existing available modules. The new EOS has been implemented in the multiphase flow simulator STOMP-CO2 developed at PNNL for simulating geological storage of carbon dioxide. Simple reservoir simulations were performed with the new module to examine decomposition of methane hydrate and formation of CO2-hydrate as a new means of natural gas production from gas hydrate reservoirs.
Numerical Modeling of Sand Production Mechanisms with Displacement Discontinuity Method
Authors: Lavrov A. , Cerasi P. , Papamichos E.
Published: December 2007

Sand production mechanisms were numerically studied by means of a displacement discontinuity boundary-element method. The method allows an explicit modelling of fracture growth in rocks in 2D. Rock fracture in hollow cylinder sand production tests was simulated. Different types of fracture growth typically observed in hollow cylinder tests were investigated, i.e. breakout formation, slit propagation and uniform collapse of the cavity. Changing the mechanical behavior of the rock, represented by the properties and constitutive behavior of the displacement discontinuity elements, from brittle to ductile resulted in a change of the failure pattern from breakouts to uniform collapse, reproducing thus the laboratory tests. A clear effect of the specimen size (external diameter) on the results was demonstrated numerically. The increase of the external diameter of the hollow cylinder results in a virtually linear increase of the hollow cylinder strength, at least in the range of diameter values investigated.
Inverted Hockey Stick Method Reveals Greater Uncertainty in Petroleum Investment Evaluations
Authors: Olsen G. T. , McVay D. A. , Lee W. J.
Published: December 2007

Conventional oil price forecasting methods in the petroleum industry typically consider uncertainty by incorporating optimistic, pessimistic, and most-likely cases. Commonly, these price projections are "hockey stick" forecasts, i.e., forecasts that are initially flat or decline for some period of time and then increase monotonically. Review of historical forecasts by industry and governmental organizations show that conventional forecasting methods often fail to capture the true uncertainty associated with oil and gas prices. Performing discounted cash flow calculations using conventional oil and gas price forecasts will therefore underestimate the uncertainty associated with project economic performance indicators. Akilu et al. developed the Inverted Hockey Stick (IHS) Method to address these shortcomings. This new method for quantifying the uncertainty of price forecasts honors the historical extremes of oil and gas prices (on a constant dollar basis) along with the maximum positive and negative historical rates of change. To investigate the uncertainty associated with economic indicators (e.g., net present value, investment efficiency, and internal rate of return), we applied the IHS method to 23 completed or proposed projects from 12 operators. We found the P50 IHS value for these economic indicators is comparable to the most-likely value from conventional price forecasts. Across all 23 cases, however, the IHS method predicted a wider range of economic indicator values than conventional forecasts. The IHS method may be preferable over conventional methods due to its ability to quantify more realistic upside and/or downside risk associated with projects in the upstream petroleum industry.
Cementing a Long Horizontal Wellbore Using CT Squeeze Technology
Authors: Rauchenstein W. , Blount C. G.
Published: December 2007

Coiled Tubing (CT) cementing has been widely used and highly successful for remedial squeeze and plug back operations for over 20 year's1,2,3. However, the vast majority of these wells were at deviations less than 90 degrees.

A long horizontal well in the Alpine field on the North Slope of Alaska was drilled early in the development phase and was out of pattern (Fig. 1). The well required a plug back and sidetracking to maintain desired off-take strategy (Fig. 2). The well was drilled to a total depth of 11,984 feet and completed with approximately 2,050 feet of 4-1/2" slotted liner inside the 2,210’ of 6-1/8" hole. Near the middle of the horizontal section, the well's deviation climbed to a maximum of 96 degrees.

Cementing operations have long been recognized as a problem in horizontal wells. However, a search of the SPE online library identified only 5 papers that mentioned the challenge we faced while a search of "horizontal" yielded 5,534 hits. Although the 5 papers did discuss the problem and gave some general guidance to cement design consideration, there was little specific information on the "best practice" approach to Plug and Abandon (P&A) long horizontal wellbores.

Based on the successful CT squeeze program in Alaska, a team of engineers and field supervisors decided to use CT cement squeeze technology to seal the lateral portion of the wellbore and leave a cement base for subsequent sidetracking operations. This paper will discuss the details of this job including: Job PlanningCement design and testingTools and EquipmentWellbore geometry and Placement detailsOnsite Job Execution detailsResultsLessons learned
Hydraulic Fracture Monitoring as a Tool to Improve Reservoir Management
Authors: Peterman F. , McCarley D. L. , Tanner K. V. , Le Calvez J. H. , Grant W. D. , Hals C. F. , Bennett L. , Palacio J. C.
Published: December 2007

We present the results of a multi-stage hydraulic fracture monitoring campaign performed during 2004 on one of Dominion Exploration and Production, Inc. producing well in the mature tight gas Sawyer field, Sutton County, Texas. The purpose of these microseismic monitoring surveys was to determine the overall geometry of the hydraulically induced fractures in the Canyon Sand formation. Information and results derived from the microseismic interpretation were used to provide the operator with recommendations for reservoir management (e.g., drilling patterns, new well placement, completion practices, etc.)

An initial borehole seismic survey confirmed optimum tool positioning to accommodate background noise and acoustic coupling. Additionally, calibration of sonic velocities was performed. All these factors led to an unprecedented level of understanding of the treated formations. All available pieces of information pertaining to the monitoring and treatment wells were combined to give a calibrated velocity model, which lead to the accurate processing of the microseismic data acquired during the one-day long hydraulic fracture operation.

The stimulation treatments utilized a titanate fracturing fluid system assisted with carbon dioxide. All six stages, except one that was surface pressure limited, were successfully placed with very little or no adjustment to the treatment design. All imaged fracture systems were oriented along the same azimuth. Larger than anticipated fracture heights were generated, and the acoustically-defined effective lateral extent of the various fracture systems was less than anticipated. Higher than designed fracture heights illustrate that it may be beneficial prior to the next design to measure specific formation mechanical parameters (e.g., in-situ stress, Young's modulus, Poisson's ratio, etc.) for simulation purposes. To minimize height development, fracturing fluids exhibiting lower fluid viscosity, injection rate adjustments, etc. have been recommended. Imaged fracture systems, all oriented along the same azimuth, suggested that present drilling pattern was inadequate for optimum drainage. Therefore, new locations for increased density drilling have been decided. Such wells are currently being drilled.

To further complement the added value of the information obtained with this data, we are performing a prorated production analysis. This will help determining effective permeability, effective fracture half-length, fracture conductivity, and skin damage factors. As well as it will allow the design, execution and evaluation cycle to be complete and provide us with lessons learned and best practices to implement in upcoming wells and operations.
Fluid-Flow Phenomena in CT Using CFD
Authors: Rosine R. , Bailey M. , Blanco I.
Published: December 2007

Coiled tubing (CT) is widely used in well intervention as a practical and cost-effective means of servicing wells. Over the years, the actual flow through CT has been a point of discussion and theory. Testing has been conducted to promote a better understanding of what happens inside the CT. In recent years, the use of computational fluid dynamics (CFD) software has provided greater insight into actual CT flow patterns, including fluid-flow velocity profiles and secondary flow regimes. These flow patterns can be studied in a straight pipe or curved (CT) condition with variable flow rates and variable fluids. CFD could help us understand the phenomenon of erosion, including particle path and migration through the tubing. It might also lead to a greater understanding and efficient design of friction pressure gradients. After CFD is proven and established, an alternative to full-scale testing or other predictive methods may be possible.

This paper discusses the flow phenomenon of CT using CFD, particularly over the tubing guide. This is an area of concern because the tubing configuration changes from straight to bent to straight again. Details of fluid flow for both the straight and curved sections have been examined to evaluate flow-velocity profiles and flow patterns. Fluids investigated have included water, gel, and slurry.
Some New Developments Applicable to Coiled Tubulars
Authors: Stanley R. K.
Published: December 2007

Complacency has little place in coiled tubulars. Here we describe the new techniques that are under investigation for both CT inspection and seamless CT production. The possibility exists to make tubulars by cold compression and to join by microwave sintering methods and amorphous bonding. The probability now exists to monitor all joining processes via the nondestructive acoustic emission technique, advanced ultrasound, and to eliminate the conventional tube-to-tube butt weld.
Environmental Assessment After Decommissioning at the Offshore North Sea - Frøy Oil Production Site: A New Field Proven Methodology
Authors: Plisson-Sauné S. , Beyer J. , Moltu U. E. , Pinturier L. , Sundt R. , Berland H. , Bjørnstad A.
Published: December 2007

The oil production at the Frøy field in the North Sea (Norwegian Continental Shelf) ceased in 2001 and the platform was removed the year after. As a supplement to the regular sediment monitoring program, an extended assessment of the "environmental condition" at Frøy has been conducted in June 2003 using biological effect parameters.

Emphasis was given on effects of drill cuttings contaminated by chemicals some of which possibly contained poly aromatic hydrocarbons.

The paper describes the operational methodology used and its cost efficiency. It also describes the know-how and the improvements gained during the field survey.

The results, presented in the paper, show the operational feasibility and the advantages of this new methodology which takes into account the effect of drilling wastes not only on sediment communities but also on other animals (fish, shrimps, etc.). They also demonstrate the absence of adverse effect of the remaining piles on the area and consequently prove that the site was released in good environmental condition for all compartments of the marine environment.
Estimation of Long Term Gas Condensate Well Productivity Using Pressure Transient Data
Authors: Osorio R. , Stewart G. , Danesh A. , Therani D. , Jamiolahmady M.
Published: December 2007

Conventional composite models can be used to calculate gas condensate well skin values including that due to condensate banking. However, the calculated skin varies in time as the fluid properties and gas and condensate fractional flow change, hence, making estimation of long term performance of a well unreliable. The dependency of gas and condensate mobility on the flow rate at near well bore conditions makes the problem more challenging. We have addressed this issue by developing an analytical method to use transient well test data to determine gas-condensate relative permeability, accounting for the rate effect, which makes future performance prediction a more reliable task.

Synthetic well test data have been generated by a commercial compositional numerical simulator with and without the rate effect. The impact of including the rate effect in the simulated cases on well test analysis results has been evaluated. The results show that for the cases analysed that the derivative of pressure responses does not necessarily always exhibit a three-radial composite behaviour due to condensate banking, when the rate effect is present, though such behaviour could be exhibited in some cases.

Our developed analytical methodology is based on a technique that allows estimating the reservoir pressure as a function of distance from the well, at the end of the drawdown period, using the bottom-hole pressure value before the shut-in. Once this reservoir pressure profile is available, the actual reservoir pressure gradient as a function of distance is determined, which can be used to calculate the values of gas and condensate relative permeability. Therefore, we show for the first time that it is possible to calculate from pressure transient data the near well gas and oil relative permeability values accounting for the rate effect. The well must be shut in at the bottom of the hole to avoid any wellbore storage effect on pressure build-up. We also show that the size of the two-phase region can be predicted with excellent accuracy using an analytical approach.