bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Mobility Ratio on the Pressure and Pressure Derivative of Wells in Closed Composite Reservoirs
Authors: Boussalem Rachid , Tiab Djebbar , Escobar Freddy H. 
Published: December 2007

Abstract
The presence of anomalies in a reservoir, such as faults or change in rock and fluid properties significantly affects the wellbore pressure behavior. An accurate reservoir description of heterogeneous reservoirs, such as a closed composite reservoir, is critical for optimizing the hydrocarbon recovery. Well test analysis provides the best technique for determining the permeability of different zones of the composite system, the skin factor, the pore volume of the inner region and the drainage area1.
The first type curves generated for a composite reservoir model appared in the literature in the early 1970s. Although these type curves were widely used for a period of time, some difficulties were found in using them. For example, the same match can be obtained on different dimensionless wellbore storage values. However, type curves were used as the basic mathematical model for several developments. Other investigations regarding the composite resevroir model with different types of applications were conducted, such as the effect of phase segragation, mobility contrast and conductivity ratio. Some researchers have mentioned the potential applications of reservoirs with a fluid bank and a burning front2-5.
In this paper an analytical model has been developed for a closed composite system. This model was validated by the numerical model already exist in the literature. An extension of conventional method and the Tiab’s Direct Synthesis technique6 are presented for a closed composite reservoir on the basis of the proposed analytical model. The effect of the mobility ratio, and radius ratio, on the pressure response has been thoroughly investigated.
A dual porosity behavior confirming the sugar-cube model is observed during the transition period for a high mobility contrast. Three important equations are derived and presented in this study: (1) An equation describing the pseudo-steady-state flow regime observed at the fingerprint of dual porosity behavior, (2) An equation describing the starting time of the pseudo-steady-state flow regime observed at the fingerprint of the dual porosity behavior, (3) An equation for the pseudo-steady-state flow regime governing the boundary effect. The formulated interpretation techniques have been tested on field cases and reasonable results have been obtained
Downhole Deployment Valve Addresses Problems Associated with Tripping Drill Pipe During Underbalanced Drilling Operations
Authors: Herbal Steve , Grant Rod , Grayson Brian , Hosie Dave , Cuthbertson Bob 
Published: December 2007

Abstract
Underbalanced Drilling (UBD) is becoming more widely used and accepted because of the many benefits it provides such as: Limitations to the formation damage common in regular overbalanced drilling.Increased rates of penetration.Increased production rates and in some cases production while drilling which can provide early cash flow and enhance economics.
However with these advantages come some drawbacks, the chief among which is the safety of the operation while tripping the drill pipe into and out of the well.
Since the well is allowed to flow in traditional UBD operations a flowing or shut in pressure results in the well. Any significant pressure at surface requires that special precautions be taken during tripping operations to control formation pressure. Several techniques can be used among which are: Killing the well, this provides for safe tripping but can obviate the very reason for using UBD - formation damage can result.Flowing the well, this can lead to a dangerous situation if a sloughing formation forms a temporary bridge in the annulus.A Snubbing unit can be employed, this enhances safety but can add considerably to the operational cost.
It is clear that a better and safer method is needed, since all the above carry disadvantages, and to this end a new method involving a downhole valve was conceived. In this approach a full opening valve which can be closed below the drill string while tripping, is deployed downhole below the "pipe light" depth and operated from surface by way of a hydraulic control bundle.
This paper will review the concept of the Downhole Deployment Valve (DDV), its design and operation. The authors will go on to provide details of the first field trial of the a 7" 26lbs/ft full opening valve in a multilateral well which was drilled underbalanced in the James Lime play in East Texas/Northwest Louisiana. They will conclude that this device can provide major enhancement to a UBD operation without in any way compromising its advantages.
A New Method of Calibrating Wireline Logs with Carbonate Core Measurements to Recognize Pay Zones
Authors: Weiss W. W. , Gottumukkala V. , Balch R. A. 
Published: December 2007

Abstract
Defining the initial water saturation in a dolomite reservoir in SE New Mexico was problematic and resulted in questions about possible oil left behind pipe after development. The application of Archie's equation was particularly suspect because of the variation in the resistivity of connate water samples.
Cores and logs were available from six wells in the Dagger Draw field and showed intersititial, fractured and vuggy porosity. A global prioritizing technique called fuzzy ranking was used to select log tracts to correlate with core measurements.
Selected log tracts then served as inputs to a neural network to develop multivariate correlations with the core measurements. The cores defined bulk volume oil, bulk volume gas, bulk volume water and aspect ratio. The focus of this paper is the estimates of bulk volume oil.
Optimal neural network architectures were developed for each of the six available well datasets. All architectures were designed to maintain a ratio of neural network weights to samples ratio less than 0.5.
Each network was blind tested against the remaining five datasets. One of the datasets with 200 whole core measurements was found to be particularly robust and was used to generate BVO logs in fourteen partially cored and uncored wells in the field.
The statistical properties sum, average, and standard deviation calculated with the BVO logs correlated with the initial oil-producing rate. Thus a new method to recognize behind pipe pay zones in a dolomite/carbonate reservoir and estimate the first years oil-producing rate was developed. The method has particular utility in finding bypassed pay for recompletion projects.
Advances in the Prediction and Management of Elemental Sulfur Deposition Associated with Sour Gas Production from Fractured Carbonate Reservoirs
Authors: Hands Nicholas , Oz Bora , Roberts Bruce , Davis Paul , Minchau Mike 
Published: December 2007

Abstract
Shell Canada has experienced significant deposition of solid sulfur during the production of dry sour gas from several of its deep carbonate pools located in Southern Alberta. In several cases, wells have become completely plugged with sulfur in the reservoir within several months. Accurate prediction and effective management of the sulfur deposition are crucial to the economic viability of these fields.
A new analytical model has been developed for predicting sulfur deposition associated with sour gas production in naturally fractured reservoirs. Key features of the model include incorporation of reservoir temperature profiles and the concept of critical velocity, which accounts for dynamic effects, resulting in a zone of reduced deposition close to the wellbore.
The model has been used to successfully match and predict sulfur deposition in several sour gas producers. The modeling results have been used as a design basis for downhole sulfur treatments and clean-out operations, the optimization of well completions and off-take rates to minimize the impact of sulfur deposition, and the development of new well designs and operating strategies for sulfur producers.
In-Situ Permeability Anisotropy vs. Depth in a Fluvial Sandstone Reservoir Using a Multiprobe Formation Tester
Authors: Domzalski S. , Boydell W. G. , Pop J. J. , Hadbi A. 
Published: December 2007

Abstract
This paper presents a case history from an Algerian fluvial sandstone oil reservoir where near to 60 in-situ measurements of permeability anisotropy, Kv / Kh, were obtained by running vertical interference tests (VITs) with a multiprobe formation tester during openhole (OH) logging operations. The formation tester, configured with four probes and a recyclable constant rate flow module performed VITs on an average 10 stations per well for several key wells in the field. The spatial displacement of the probes along the wellbore at each test station enabled simultaneous overlapping measurements of permeability anisotropy on 0.70 meter and 3 meter length scales (similar to vertical grid block sizes used in field reservoir simulators). These measurements provided Kv / Kh ratios in homogeneous "clean" sections of sedimentary units and information on sealing properties through the determination of the effective Kv / Kh of tight streaks, shales, laminations and "dirty" sections straddled by the probes.
The various steps in the data acquisition chain are discussed, including the prejob VIT feasibility simulation runs and the choice of modules for the formation tester tool. Also described is the onsite decision-making process for choosing VIT stations based on the petrophysical and geological imaging wireline logs and classic formation tester pretest data. On-site quick-look data interpretation and subsequent interpretation results of several VIT stations along with core-derived values averaged over the VIT measurement scale are presented.
With careful job planning and execution the case history shows that it is possible to obtain multiple in-situ permeability anisotropy measurements in a geologically consistent manner during OH logging operations.
CO2 Enhanced Gas Recovery Studied for an Example Gas Reservoir
Authors: Clemens Torsten , Wit Krijn 
Published: December 2007

Abstract
In the wake of the Kyoto protocol, CO2 emission reduction to control the level of CO2 in the atmosphere has become an important goal. One possibility of reducing greenhouse gas emission is to separate and inject CO2 from gas fired power plants into gas fields.
To investigate the effects of CO2 injection on methane recovery, five different CO2 injection strategies were investigated for an example gas reservoir. The injection scenarios included installation of a Zero Emission Power Plant (ZEPP) at surface, supplying the reservoir with a constant CO2 rate over 25 years.
Installation of a ZEPP enabled using a lower tubing head pressure than for gas delivery to the gas distribution grid resulting in accelerated methane production. For most of the cases investigated, the cumulative methane production was increased as well. CO2 breakthrough occurred between 3 and 15 years. The CO2 which was produced in the production wells was fed into the ZEPP and re-injected with the newly generated CO2.
The highest incremental gas recovery was obtained for the case of conventional depletion of the gas reservoir until abandonment and subsequently injection of CO2, leading to enhanced gas recovery. The maximum incremental gas recovery was about 10 % of Gas Initially In Place (GIIP). For the case of injection of CO2 early in the life of the gas field, the methane recovery was decreased compared with conventional gas production by depletion.
Drilling Parameter Selection for Well Quality Enhancement in Deepwater Environments
Authors: Kravis S. , Irrgang R. , Phatak A. , Martins A. , Nakagawa E. 
Published: December 2007

Abstract
The study of overall well quality is a neglected area of the industry. Aspects such as formation damage, drilling interactions, and hole rugosity tend to be treated separately in the literature. This paper describes a software tool that uses stored well data and drilling experiences to produce an overall set of well quality metrics that facilitate the assessment of drilling and completion performance in a given field. The tool is particularly useful for risk assessment when drilling complex trajectories and for improving the design of new deepwater wells.
Modeling, Simulation and Comparison of Models for Wormhole Formation During Matrix Stimulation of Carbonates
Authors: Panga Mohan K. R. , Balakotaiah Vemuri , Ziauddin Murtaza 
Published: December 2007

Abstract
A new averaged/continuum model is presented for simulation of wormhole formation during matrix stimulation of carbonates. The model presented here differs from existing literature models in three fundamental aspects. First, we show that the dissolution process creates a Darcy velocity field with non-zero divergence. Second, we use two concentration variables to account for the local gradients at the pore level caused by the coupling between the flow, species diffusion and chemical reaction. Third, we account for both the asymptotic/diffusive and convective contributions to the local mass transfer coefficient between the fluid and solid. We argue that models that do not account for these effects do not retain the qualitative features of the reactive dissolution process and hence cannot be predictive. The averaged model developed here accounts for pore level physics by coupling the local pore scale phenomena to the macroscopic variables (Darcy velocity, pressure and reactant cup-mixing concentration) through the structure-property relationships (permeability-porosity, average pore size-porosity and interfacial area-porosity), and the dependence of the fluid-solid mass transfer coefficient and fluid phase dispersion coefficient on the evolving pore scale variables (average pore size and local Reynolds and Schmidt numbers).
A preliminary analysis of the model is presented and the influence of various factors on flow channeling is examined using the new model. The model predictions are compared with the available laboratory data.
Produced Water Regulations in the United States: Then, Now and in the Future
Authors: Caudle Dan D. 
Published: December 2007

Abstract
The discharge of produced water into surface waters has been regulated since the late 1960's. The regulations prohibit discharge of any water that would cause permanent harm to the environment and sets limits on waters that are discharged based on best available technology for removing regulated contaminants. The United States is subdivided into categories under United States Environmental Protection Agency (EPA) regulations. Discharge limits in the subcategories range from no discharge to surface waters to discharges limited by toxicity and oil content. Discharge limits are determined by available technology for controlling toxicity and oil and grease.
This paper reviews the development of the guidelines and limits on produced water discharges and the technology to meet the regulatory limits for each category. It also discusses the problem of new exploration areas that might not fit into a one of the existing categories. As the exploration production industry advances, it is moving into areas such as very deep water that may have different technology constraints than those addressed by past regulations. Currently each subcategory has limits determined by technology appropriate to that subcategory. If future exploration areas do not fit into a recognized category, what should be done? For example, in very deep water, is a new subcategory needed with limits appropriate to water treating technology that can be economically applied in that environment?
Numerical Simulations of NMR Responses for Improved Interpretations of NMR Measurements in Reservoir Rocks
Authors: Øren P. E. , Antonsen F. , Rueslåtten H. G. , Bakke S. 
Published: December 2007

Abstract
We reconstruct the three-dimensional (3D) microstructure of Fontainebleau sandstone samples of different porosities by a process-based reconstruction method. Permeabilities of the reconstructed media are computed by solving the Stokes equations, while the formation factors are computed by solving a Laplacian equation. Nuclear Magnetic Resonance (NMR) responses are determined by a random walk simulation, and the results are compared with experimental data. Permeabilities estimated from commonly used NMR correlations are compared with the computed permeabilities. The comparison shows that the accuracy of the NMR-derived permeabilities can be improved significantly by accounting for tortuosity effects and variations in surface relaxivity.
Knowledge Discovery in Databases and Multiphase Flow Metering: The Integration of Statistics, Data Mining, Neural Networks, Fuzzy Logic, and Ad Hoc Flow Measurements Towards Well Monitoring and Diagnosis
Authors: Alimonti C. , Falcone G. 
Published: December 2007

Abstract
The usual approach to the interpretation of producing wells is based on mechanistic models for the simulation of steady state and transient flow regimes. However, there are significant reservations about convergence problems, computational limits, the need for extensive tuning on field data, the instability of boundary conditions, the limited applicability of existing multiphase flow models, and the uncertainties associated with choke valve models. The current industry standards are critically reviewed within this framework.
The real-time monitoring of producing wells is recognised as the best way of optimising field performance. Monitoring a producing well implies the ability to track, in real-time, any changes in fluid composition, flow rates, or pressure and temperature profiles. Multiphase Flow Metering (MFM) plays a key role in this scenario. Such information, combined with the critical analysis of historical data from the well itself or from analogue wells, allows diagnosis of the system and prediction of future trends. However, field data per se ’ do not necessarily generate knowledge. This is particularly true for large databases, which are difficult to manipulate to provide suitable inputs for wellbore simulators.
This paper suggests how MFM, Knowledge Discovery in Databases (KDD) and Fuzzy Logic (FL) can offer an alternative approach to the analysis of producing wells. KDD is the automated extraction of patterns representing knowledge implicitly stored in large information repositories. Distributed, ad-hoc field measurements (including MFM and downhole measurements) can be processed via data cleaning, data integration, data mining, artificial intelligence, and pattern evaluation. FL can then manage the resulting information in terms of flow assurance and production optimisation.
The same techniques can also be extended to the reservoir and the production network, for an integrated approach to production system analysis.
Relative Permeability Modifier and Scale Inhibitor Combination in Fracturing Process at San Francisco Field in Colombia, South America
Authors: Castano R. , Villamizar J. , Diaz O. , Avila M. , Gonzalez S. , Dalrymple E. D. , Milson S. , Everett D. 
Published: December 2007

Abstract
Water production in the San Francisco field in Colombia is characterized by a severe carbonate scaling tendency, particularly in the lower Caballos zone. Following several fracture stimulation treatments which incorporated RPM (Relative Permeability Modifier) in San Francisco field, it was observed that, although the RPM decreased the anticipated water production, there was an undesirable effect in regard to scaling problems. Some wells ended up losing a portion of the increased production which had been gained by using the RPM fracturing process. This decrease in production was attributed to carbonate scaling after the wells were back on production for several months.
A well candidate was chosen (San Francisco 60) and laboratory flow tests were performed in representative cores to determine if a detrimental impact would occur in regard to the ability of the RPM to function properly when the scale inhibitor was part of a combined treatment. Based on these results, a combined fracturing treatment which incorporated a water reduction agent (RPM) in combination with a scale inhibitor was performed in the SF 60 well. To our knowledge, this was the worlds first combined application of an RPM and scale inhibitor in a hydraulic fracture treatment. Further, this new systematic approach to two very difficult problems yielded excellent results: Following the treatment, the well increased production by almost 10 fold while at the same time, water cut was reduced by 30%. This procedure reduced the cost of water management and associated scaling problems, which had been common in this field. This new system has created many more fracture stimulation opportunities which in the past had not been considered economically attractive.
The work described in this paper is the result of a true team effort (operator/Service company) and describes the focus in solving several production problems (as experienced in San Francisco field) which resulted in a multi-purpose treatment. The net result of the method developed is fewer required stimulation/workover jobs while maintaining the same or increased hydrocarbon production, and less water (which also translates into lower lifting costs).
This paper will present the following:
Data illustrating the type of production problems being experienced in the San Francisco field The results of approaching the water production issues and scaling tendencies individually The laboratory evaluation techniques and data obtained when combining the individual treatments into a "system" The resulting "job design," treatment, and production response when the combination stimulation/water control/scaling treatment was actually put into practice.
Chemical and Physical Characterization of Aphron-Based Drilling Fluids
Authors: Ivan Catalin D. , Growcock Frederick B. , Friedheim James E. 
Published: December 2007

Abstract
The depleted reservoirs in many of the world's mature fields contain hidden problems that can make further development unprofitable. Some zones are typified by water-wet sands that frequently trigger costly seepage losses and differential sticking. Others are characterized by laminated sand and shale sequences, which create the conditions for slow, dangerous and unduly expensive drilling when conventional rig equipment is used. If operators turn to underbalanced drilling as an alternative, the extra time and equipment required for safe operation can seriously degrade project economics in some applications.
Aphron-based systems are engineered drilling-fluids that aid in well construction by controlling losses in depleted, high-permeability sands while stabilizing pressured shales. One of the more attractive features of an aphron-based system is that it does not require any of the extra equipment used in air or foam drilling. There are no compressors, high-pressure hoses or connections to add costs and safety concerns. The system uses conventional fluid-mixing equipment to form tough, flexible micro-bubbles.
Once formed, these micro-bubbles, or "aphrons," differ from the bubbles produced in air or foam drilling in two significant ways. First, aphrons resist coalescence into larger bubbles. The aphrons are attracted to lower-pressure regions in the formation but remain discreet from each other, forming a strong network of individual micro-bubbles. Second, aphrons are tough and stable. They are comprised of a core of air surrounded by layers of a proprietary polymer and a tensoactive additive.
The authors will detail the chemical and physical characteristics of aphron-based drilling fluids that make them uniquely qualified to solve some operational problems.