bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coiled-Tubing Drilling: Continued Performance Improvement in Alaska
Authors: McCarty Thomas M. , Stanley Mark J. , Gantt Lamar L. 
Published: December 2007

Summary
Coiled-tubing drilling (CTD) has thrived in recent years on the North Slope of Alaska. To date, CTD has sidetracked more than 250 wells in a continuous program of activity since 1995. In that time, Alaska has become a proving ground for CTD tools and techniques. CTD has matured into a highly efficient and economical means of sidetracking wells on the North Slope. Key reasons for the success of the program include continuous use, which allows rapid learning; a culture of technical innovation; effective performance-based service contracts; the right people with the right expertise; and the vision and support of senior management. This paper summarizes the performance improvements realized in North Slope CTD operations, detailing how the tools and techniques have changed.
Applying new technologies and improving existing tools are major levers of CTD progress. Major performance improvement areas include window milling, bottomhole assembly (BHA) reliability, and lost circulation. Reliability improvements in equipment and persistent innovation will continue to fuel CTD's underlying economic performance in Alaska.
Included in this paper is a discussion of the remaining problems associated with through-tubing, slim-hole drilling with CTD technology. Examples of new CTD technologies being used or about to be implemented in Alaska will also be presented.
Multiscale Data Integration Using Markov Random Fields
Authors: Lee Sang Heon , Malallah Adel , Datta-Gupta Akhil , Higdon David 
Published: December 2007

SummaryWe propose a hierarchical approach to spatial modeling based on Markov Random Fields (MRF) and multiresolution algorithms in image analysis. Unlike their geostatistical counterparts, which simultaneously specify distributions across the entire field, MRFs are based on a collection of full conditional distributions that rely on the local neighborhoods of each element. This critical focus on local specification provides several advantages: (a) MRFs are computationally tractable and are ideally suited to simulation-based computation, such as Markov Chain Monte Carlo (MCMC) methods, and (b) model extensions to account for nonstationarity, discontinuity, and varying spatial properties at various scales of resolution are easily accessible in the MRF framework. Our proposed method is computationally efficient and well suited to reconstruct fine-scale spatial fields from coarser, multiscale samples (based on seismic and production data) and sparse fine-scale conditioning data (e.g., well data). It is easy to implement, and it can account for the complex, nonlinear interactions between different scales, as well as the precision of the data at various scales, in a consistent fashion. We illustrate our method with a variety of examples that demonstrate the power and versatility of the proposed approach. Finally, a comparison with Sequential Gaussian Simulation with Block Kriging (SGSBK) indicates similar performance with less restrictive assumptions.
Simulation of Hydraulic Fracturing Processes
Authors: Settari A. 
Published: December 2007

AbstractA mathematical model of the fracturing process, coupling the fracture mechanics and fracture propagation with reservoir flow and heat transfer, has been formulated. The model is applicable to fracturing treatments as well as to high leakoff applications such as fractured waterfloods and thermal fractures. The numerical technique developed is capable of simulating fracture extension for reasonably coarse grids, with truncation error being minimized for high leakoff applications when the grid next to the fracture is approximately square. With the aid of the model, a generalization of Carter's propagation formula has been developed that is also valid for high fluid-loss conditions. The capabilities of the model are illustrated by examples of heat transfer and massive-hydraulic-fracturing (MHF) treatment calculation.
Full-Field Modeling Using Streamline-Based Simulation: Four Case Studies
Authors: Baker R.O. , Kuppe F. , Chugh S. , Bora R. , Stojanovic S. , Batycky R. 
Published: December 2007

Summary
Modern streamline-based reservoir simulators are able to account for actual field conditions such as 3D multiphase flow effects, reservoir heterogeneity, gravity, and changing well conditions. A streamline simulator was used to model four field cases, with approximately 400 wells and 150,000 gridblocks. History-match run times were approximately 1 CPU hour per run, with the final history matches completed in approximately 1 month per field. In all field cases, a high percentage of wells were history matched within the first two to three runs.
Streamline simulation not only enables a rapid turnaround time for studies, but it also serves as a different tool in resolving each of the studied fields' unique characteristics.
The primary reasons for faster history matching of permeability fields using 3D streamline technology as compared to conventional finite-difference (FD) techniques are as follows:
Streamlines clearly identify which producer-injector pairs communicate strongly (flow visualization). Streamlines allow the use of a very large number of wells, thereby substantially reducing the uncertainty associated with outer-boundary conditions. Streamline flow paths indicate that idealized drainage patterns do not exist in real fields. It is therefore unrealistic to extract symmetric elements out of a full field. The speed and efficiency of the method allows the solution of fine-scale and/or full-field models with hundreds of wells. The streamline simulator honors the historical total fluid injection and production volumes exactly because there are no drawdown constraints for incompressible problems. The technology allows for easy identification of regions that require modifications to achieve a history match. Streamlines provide new flow information (i.e., well connectivity, drainage volumes, and well allocation factors) that cannot be derived from conventional simulation methods.
Automatic Decline-Curve Analysis of Wells in Gas Reservoirs
Authors: Hagoort Jacques 
Published: December 2007

Summary
A method is presented for automatic decline-curve analysis (DCA) of wells in gas reservoirs. It is based on the production behavior of a vertical well in a finite, plane reservoir containing dry gas. The method accounts for pressure-dependent gas properties, covers both transient and boundary-dominated flow, and can accommodate varying wellbore pressures. The physical parameters that govern the production behavior are estimated by nonlinear regression of observed-rate data. Interpretation of the transient flow period yields flow capacity (kh) and skin factor; the boundary-dominated flow period provides well index (WI) and gas initially in place (GIIP). Future production rates can be estimated for operating conditions other than those that prevailed during the historical production period. These estimates also may include upper and lower bounds for a given confidence level. The method is illustrated by a synthetic and a real-life example of a declining production well.
Cuttings-Transport Problems and Solutions in Coiled-Tubing Drilling
Authors: Leising L. J. , Walton I. C. 
Published: December 2007

SummaryIn spite of the many technological advances that have accompanied the growth of coiled-tubing (CT) drilling, one significant challenge remains—effective cuttings transport, particularly in deviated wells. This paper presents a summary of cuttings-transport problems and current solutions. It is shown that, in many circumstances, hole cleaning is more efficient if a low-viscosity fluid is pumped in turbulent flow rather than a high-viscosity fluid in laminar flow. Case studies are presented that illustrate both cuttings-transport problems and routine applications without cuttings-transport difficulties. The proposed hole-cleaning models are used to interpret these data and to suggest possible alternative approaches.Two novel approaches to understanding hole cleaning are introduced. First, for laminar flow, the distance that a particle will travel (downstream) before it falls across the annulus clearance is calculated with Stokes’ law and the local viscosity while flowing. This analysis may easily be applied to optimize mud selection and wiper trips. Applying this model to high low-shear-rate-viscosity (LSRV) gels shows that they may perform well inside casing but are expected to do a poor job of hole cleaning in a narrow, openhole, horizontal annulus without rotation. Second, for turbulent flow in horizontal wells, the concept of using annular velocity (AV) as a measure of hole cleaning is shown to be insufficient. A more complete term, annular velocity/root diameter (vARD), is introduced and should be used to compare cuttings transport in turbulent flow in horizontal wells of different cross-sectional areas.
Financing the U.K. North Sea
Authors: Ross Ian W. 
Published: December 2007

The amount of financing required for developing the U.K. North Sea must be found from internal and external sources. This paper examines (1) major sources and reasons why some methods are preferable to others and (2) alternatives that are available depending on the size and financial strength of the developer and the relative risks of the projects.

Introduction
Although estimates vary, it is forecast reliably that spending on North Sea exploration and production will continue at a rate of $5 billion a year through 1985, and from that date at a rate more or less depending on U.K. government policy and exploration results. To quantify the costs in a different way, this is the equivalent of $10,000/bbl of peak daily production. When we balance this cost against the 5 to 10 years taken to develop North Sea fields, it is evident that there is a long lead time before any cash flow and, hopefully, profit pass back to the project owners. project owners. These vast sums of money have been and will continue to be raised from a number of sources. I will examine in this paper the types of financing available and cite various alternatives that companies already have used to raise funds for development. In view of the differing regulatory and tax regimes in each of the Norwegian, Danish, Dutch, French, and U.K. sectors of the North Sea, I will limit my paper to the biggest in terms of current expenditure--the U.K. sector.

Financing Sources
The major sources of financing for the North Sea to date have been the internal cash flow of the license holders, export credits and "interest relief grant" financing, and bank financing. Undoubtedly, for some of the large companies, internal financing will continue to be a major source of funding, and the long-term capital markets will provide another source, probably for those same companies. In many cases, however, the bank market will be a major source of funds, and given the quantitative ability of the market and its flexibility, bank financing is likely to continue providing a substantial portion of the funds required. In fact, one may even argue that, given the increasing investment needs of the oil industry and its increasing reliance on external financing, the banking community will be called upon to provide a larger proportion of the expenditures than it has to date.

Types of Bank Financing
Bank financing can be divided into two categories, the major distinction between them being the degree to which the lender looks directly to the general credit of a company as the source of repayment. The methods can be applied equally for the development of an oil or gas field and are basically the same for a single company as for a consortium.The first category can be called "balance sheet financing" and consists of borrowings based solely on the financial strength of the borrower.
JPT
P. 306
Best Practices and Methods in Hydrocarbon Resource Estimation, Production and Emissions Forecasting, Uncertainty Evaluation, and Decision Making
Authors: Jonkman R.M. , Bos C.F.M. , Breunese J.N. , Morgan D.T.K. , Spencer J.A. , Søndenå E. 
Published: December 2007

Summary
On behalf of a group of sponsors consisting of the Norwegian Petroleum Directorate (NPD) and most E&P companies active in Norway, a work group was established to author a report on the best practices and methods in hydrocarbon resource estimation, production and emissions forecasting, uncertainty evaluation, and decision making. The work group is part of Norway's forum for Forecasting and Uncertainty evaluatioN (FUN).
Following a detailed data acquisition and interviewing phase used to establish an inventory of the current practice of all sponsors involved, the work group postulated a relationship between a company's practices and its economic performance. A key distinguishing factor between companies is the degree to which probabilistic methods are adopted in integrated multidisciplinary processes aimed at supporting the decision-making process throughout the asset life cycle and portfolio of assets.
Companies have been ranked in terms of this degree of integration, and best practices are recommended. In many companies, a gap seems to exist between available and applied technology. Data and (aggregated) information exchange between governments and companies is also discussed. A best practice based on their respective decision-making processes is recommended.
Evolutionary Algorithms Applied to History Matching of Complex Reservoirs
Authors: Schulze-Riegert R.W. , Axmann J.K. , Haase O. , Rian D.T. , You Y.-L. 
Published: December 2007

SummaryConventional direct optimization methods and evolutionary algorithms are applied to the problem of history matching in reservoir engineering. The advantage of parallel computing for the optimization of complex reservoir models is investigated. Methods to improve the convergence of evolutionary algorithms by introducing prior information are applied.The potential of using optimization methods for the problem of reservoir modeling in various modeling phases is discussed. The methodology is illustrated on realistic simulation cases. In conclusion, results suggest that evolution strategies can be applied successfully to generate possible solutions in the early modeling phase.
Formation Damage Abatement: A Quarter-Century Perspective
Authors: Ghalambor Ali , Economides M. J. 
Published: December 2007

SummaryPetroleum well production impairment has long been associated with formation damage. Concepts such as the skin effect and its various manifestations have been introduced to account for the effects of damage. The origins of damage and the types of damage also have been the subjects of intense scrutiny. Abatement has included preventive measures such as the use of nondamaging fluids, presumably more benign processes, and improved drilling and well construction procedures and techniques. Once in place, the removal of damage has spawned an entire industry, that of matrix stimulation. This involves the use of appropriate remediation fluids, complete with the understanding of the often contrasting interaction among these fluids, the fluids and the damage, and, very importantly, the side effects that can damage the well more than its prestimulation state. Again, appropriate hardware was necessary. Owing to the fact that damage removal is often either incomplete or unsuccessful, methods of bypassing the damage, such as high-permeability fracturing, have been developed. Finally, brute force approaches are common, including the drilling of more vertical and/or horizontal wells regardless of the damage in order to get enough production. This paper is a critical review of both the evolution of the technologies and the thought processes that have permeated the industry over the past quarter century. Particular emphasis is given to the resolution of controversial subjects and their impact on the field. These include issues such as matrix stimulation vs. fracturing, sand production control vs. sand deconsolidation management, underbalance vs. extreme overbalance, and perforating and drilling fluids and practices.
Bottom-Hole Pressure Reduction Due to Gas Cut Mud
Authors: White Robert J. 
Published: December 2007

Abstract
Strong's equation for calculating bottom-hole pressure reduction due to gas cutting of drilling mud is corrected, resulting in a simpler equation which is easier to use. Use of the equation is illustrated by examples. It is shown that reduction of weight of a 10 lb/gal mud by 50 per cent at the surface due to gas cutting produces only a 3 per cent decrease in hydrostatic head at the bottom of a 5,000-ft well. It is also shown that at the surface 5 volumes of air per volume of mud are required to reduce the apparent mud weight from 8.5 to 6.5 lb/gal in a 3,000-ft well. Illustrative graphs are included to show the effect of various degrees of gas cutting on apparent mud weight at depths of 2,000, 5,000 and 10,000 ft and to show variation of apparent mud weight, with depth for a 100 lb/cu ft (13.37 lb/gal) mud gas cut to 90 lb/cu ft (12.03 lb/gal) at the surface.

Introduction
In 1938, Strong published the following equation for calculating reduction in bottom-hole pressure due to gas cutting of drilling mud.
This equation was recently found to contain an error due to an incorrect expression for variation of volume fraction of gas with pressure. Values calculated by the original equation are close to the correct values for small percentages of gas for which it was derived but become increasingly erroneous as the gas content increases and are completely unusable at the very high gas contents employed in aerated mud.
Characterizing the Greater Burgan Field: Use of Geochemistry and Oil Fingerprinting
Authors: Kaufman R. L. , Dashti H. , Kabir C. S. , Pederson J. M. , Moon M. S. , Quttainah R. , Al-Wael H. 
Published: December 2007

Summary
This study reports reservoir geochemistry findings on the Greater Burgan field by a multidisciplinary, multiorganizational team. The major objectives were to determine if unique oil fingerprints could be identified for the major producing reservoirs and if oil fingerprinting could be used to identify wells with mixed production because of wellbore mechanical problems. Three potential reservoir geochemistry applications in the Burgan field are: (1) evaluation of vertical and lateral hydrocarbon continuity, (2) identification of production problems caused by leaky tubing strings or leaks behind casing, and (3) allocation of production to individual zones in commingled wells. Results from this study show that while oils from the major reservoir units are different from each other, the differences are small. Furthermore, a number of wells were identified in which mixed oils were produced because of previous mechanical problems. Both transient pressure testing and distributed pressure measurements provided corroborative evidence of some of these findings. Other data show that Third Burgan oils are different in the Burgan and Magwa sectors, suggesting a lack of communication across the central graben fault complex. This finding supports the geologic model for the ongoing reservoir simulation studies. Success of the geochemistry project has spawned enlargement of the study in both size and scope.
Application of a New Multicomponent Gas Adsorption Model to Coal Gas Adsorption Systems
Authors: Clarkson C. R. 
Published: December 2007

Summary
A new multicomponent adsorption model is proposed for application to coal gas adsorption systems. The model is derived by combining the vacancy solution and Dubinin-Polanyi theories. Applications of the new adsorption model include the modeling of multicomponent adsorption processes associated with primary and enhanced coalbed methane recovery (ECBM).
In the new model, the adsorbed phase in the single-component (pure) adsorption system is treated as a binary mixture of a singlecomponent gas with a hypothetical "vacancy" species, which also occupies adsorption space. The adsorption system is modeled as equilibrium between the gaseous phase and the adsorbed-phase vacancy solution. The Dubinin-Astakhov (D-A) equation is used to generate activity coefficients, as a function of the degree of porefilling, for the pure component gas in the binary (adsorbate+vacancy) adsorbed-phase mixture. The Wilson equation is chosen to fit pure component (D-A-derived) activity coefficient curves by optimizing the binary interaction coefficients. These binary interaction coefficients are then used to predict multicomponent adsorption equilibrium, although only the case of binary adsorption is modeled here.
The adsorbed phase mixture for binary gas adsorption is treated as a ternary mixture of the two pure component adsorbates and the hypothetical vacancy species. Binary gas adsorption equilibrium is described by equilibrium between the gaseous components and the components in the adsorbed phase solution. Adsorbed-phase activity coefficients are calculated from the Wilson equation, with the binary interaction coefficients obtained from pure component adsorption data. Thus, only pure component adsorption data are required to make binary and multicomponent adsorption predictions with the new model.
Two binary (CH4+CO2) gas adsorption experimental data sets with coal as the adsorbent and one binary (CH4+C2H6) gas adsorption data set with activated carbon as the adsorbent are used to test the predictions of the new model. In most cases the new model is able to predict binary gas adsorption accurately. The poor fit of the Wilson equation to the D-A-derived activity coefficients for some pure component data suggests that some improvement in model predictions could be made with the choice of a different activity coefficient equation.
A unique feature of the current model is the ability to predict multicomponent gas adsorption at different temperatures from the pure component adsorption data collected at a single temperature. The temperature independence of pure component "characteristic" curves, as demonstrated in Dubinin-Polanyi theory, allows pure component adsorption to be predicted for a range of temperatures. These pure component data can then be used in modeling binary or multicomponent adsorption data at various temperatures. This is demonstrated for one experimental binary gas adsorption data set.