bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Neural Networks to Estimate Monthly Production: A Case Study for the Devonian Carbonates, Southeast New Mexico
Authors: Schrader S. M. , Balch R. S. , Ruan T.
Published: December 2007

Neural networks are a well developed computational intelligence technology with many possible applications in the oil and gas industry. For this study a neural network was developed to predict production potential for a single formation, prior to drilling, over a 16,000 square mile area of SE New Mexico. The process involved gathering data for use as potential inputs, collecting production data at known wells, selecting optimal inputs, developing and testing various network architectures, making predictions, analyzing and applying the results.

Variables considered as potential inputs included the thickness of the primary source rock (Woodford shale), total organic carbon (TOC), production index (PI), paleo thickness, curvature of paleo structure, and permeability. Two variables were derived; the product of Woodford thickness, TOC and PI, termed generative potential, and the log of generative potential. Variables were interpolated using kriging over the study area.

The neural network was trained to identify the production at a set of wells with attempted production from the formation. Production was measured in barrels of oil equivalent per month (BOEPM) averaged over the first year 12 months of production. The data included producing wells and dry holes.

Potential input variables were tested against the output to determine the best variables for training. First, a fuzzy ranking algorithm selected Woodford thickness and TOC. A secondary correlation study also recommended Woodford thickness and TOC, and added permeability and generative potential.

A series of neural networks were developed to test different architectures. The architectures were compared based on the r2 correlation while considering the possibility of overtraining based on the size of the input variable set. Random subsets of data were excluded for blind testing. A 4-6-1 architecture with an r2 correlation of 0.84 was selected. The neural network was re-trained multiple times achieving consistent correlations in each test.

Once trained, the network was used to predict production over the entire region. This predicted production was further refined by excluding production at locations where the Woodford shale was not present. Results were evaluated by inspecting a map of predicted production and performing statistical testing, including a correlation of predicted and actual production, which produced a correlation coefficient of 0.79. The results were then used by the Devonian FEE Tool, an expert system designed to reduce exploration risk.
Increased Production Results from Pilot Horizontal Waterflood in Osage County, Oklahoma
Authors: Westermark R. V. , Schmeling J. , Dauben D. , Robinowitz S. , Weyland H. V.
Published: December 2007

This paper details the results of a three-year project to test horizontal waterflooding as a means of improving oil recovery from the Bartlesville sandstone in an abandoned 100-year-old oil field in Osage County, Oklahoma. Supported by a grant from the Department of Energy (DOE), this work was conducted by Grand Resources, Inc., an independent operator in Tulsa, Oklahoma. The project was initiated based on the concept of using three parallel horizontal wells (an injector straddled by two producers) in a heel-to-toe configuration. The pilot test evolved into an oil rim recovery project with pressure support coming from a vertical injection well, due to reservoir heterogeneities and lower-than-expected oil saturations.

Key technical aspects are discussed, including reservoir screening and the selection process; substantiating the primary and secondary production history; interpreting the depositional environment, including natural fracture orientation and a wellbore stability evaluation. Reservoir characterization is initially based on vertical logs and is modified when horizontal openhole logs become available. Characterization provides the details necessary for the reservoir simulation used to predict oil recovery and assess the economic viability. The simulation process is ongoing and updated as additional data is acquired.

Once waterflooding operations have begun, the technologies and methods employed to evaluate, manage and adjust both injection and production performance include: Evaluating production results.Conducting step rate and injection profile tests in the horizontal injection well.Running a full suite of open hole logs through the short radius curve, including an acoustic borehole televiewer, to determine fracture frequency and orientation.Adjusting injection water volume to assist in reducing operating expenses yet maintain adequate reservoir pressure support for high fluid withdrawal rates.Re-drilling the horizontal producing wells closer to the top of the reservoir to significantly increase the oil cut.

The short radius drilling system is explained, in addition to the drilling of the lateral wellbores.

Oil recovery from the originally designed pilot was disappointing due to the unexpectedly high water saturations that were encountered. However, results from the modified pilot are much more encouraging, with 15 to 20 BOPD being produced from a thin oil column overlaying water.
Developing the Obaiyed Tight Gas/Condensate Field, Egypt – A Case Study
Authors: Strating E. H. H. , Amin S. , Samiee R. A. , Shanab M. A. , Ebied M. , Samaie A. A. , Ali N. M.
Published: December 2007

The Obaiyed tight Gas-Condensate field was discovered in 1992 and following 4 appraisal wells and 3 additional exploration wells the first integrated field development plan was issued in 1996. This formed the basis for an agreement to deliver 300 MMscf/d. The field was brought on stream in 1999 reaching full capacity in 2001. However, reservoir pressures dropped much faster than expected (30% rather than expected 10% annual production decline). In addition condensate production only reached 60% of initial expectation levels.

A complete subsurface review in 2000-1 showed 5 key areas of concern that requiring specific attention in the FDP update: [1] more severe reservoir compartmentalisation, [2] poorer reservoir quality in NW part of the field, [3] lower CGR's, [4] Temperature constraints on flow lines, [5] Multiple fluid contacts. Consequently expected production levels and recovery factors had to be adjusted downward. A root cause underlying most of these issues (points [1], [3], [4], and in part [5]) can be traced back to the design and duration of the early well tests.

Three years after the integrated review the reservoir/well behavior is very much in line with the 2001 model, indicating the quality work done at the time.

Based on the above solid models, the future development of the field has been optimized. It comprises the following key activities: Improved field & reservoir managementFull field booster-compressionProduction accelerationUnder Balanced Drilling

The aim of the paper is to present the Obaiyed Field Development case, lessons learnt, remedial action taken and future plans.
Pickling Well Tubulars Using Coiled Tubing: Mathematical Modeling and Field Application
Authors: Al-Mutairi S. H. , Hill A. D. , Nasr-El-Din H. A.
Published: December 2007

Coiled tubing is usually used to conduct acid pickle treatments. The purpose of the treatment is to prevent pumping damaging materials into the formation prior to the main acid job. In this case, the acid is pumped down the coiled tubing, and then flowed up through the tubing-coiled tubing annulus. Pickling is a process of flow with heterogeneous reactions occurring with mill scale (Fe3O4) and other contaminants at both the inner wall of the production tubing and the outer surface of the coiled tubing.

Pickling is an essential part of well stimulation treatments if the main treatment fluids (acidizing, fracturing, gravel packing, etc.) are to be bullheaded. However, it appears that traditional pickle practices are overestimating the required acid volume and/or concentration. Field data indicated that excessive acid volumes are used for tubing pickle because large returns of unreacted acid are usually recovered on the surface.

In this paper, mechanisms to explain the behavior of acid contact with the tubing are presented and a model for predicting acid consumption and dissolution of tubular contaminants is developed. The model includes reactions of acid with mill scale. A system of non-linear partial differential equations is developed and the equations are solved numerically to predict the concentrations of major species as a function of axial position along the tubing and in the effluent from the well during flowback.

Field application included pickling of low-carbon steel tubing (11,900 ft of 5.5-inch C-95) using coiled tubing. A slug of 5,000 gals of 20 wt% HCl with additives was used. Samples were collected from the treated well during the flowback of pickling treatment. The model was used to predict the concentrations of various species in the well flowback samples. Model predictions for acid, chloride ion, and total iron concentrations were in good agreement with field results. In addition, the model proved to be a valuable tool in optimizing future pickling treatments.
Smart Operations: Cheap? High-tech? Or Simply the Best Fit? Optimized Drilling Solutions on the South Pars Field, Offshore Iran
Authors: Johannessen B. , Vestvik J.
Published: December 2007

In this paper we will discuss the drilling optimizations implemented in the South Pars field, which has resulted in one year of saved rig time.

We will cover the improvements introduced to the drilling process and also the technologies and equipment utilized to achieve the success so far; such as optimized well trajectories for performance drilling, introduction of PDC bit technology in combination with ultra high powered steerable motors, cementing techniques and drilling fluid optimization.
Flow-Rate Optimization of Aerated Fluids for Underbalanced Coiled-Tubing Applications
Authors: Ozbayoglu M. E. , Omurlu C.
Published: December 2007

Coiled tubing (CT) is widely associated with underbalanced drilling technologies. Especially in depleted reservoirs, drilling need for underbalanced and extended reach wells is increased where CT is widely used. In this work, optimization of volumetric requirements for liquid and gas phases is investigated in long horizontal and inclined sections of CT applications for underbalanced drilling. A mathematical model is introduced in order to predict the flow characteristics of multiphase flow through an annulus. Flow patterns and frictional pressure losses are evaluated using the experimental data of a wide range of liquid and gas flow rates recorded at a field-scale annular flow loop with common CT drilling dimensions as well as circular pipes. Practical curves are developed for determining the optimum flow rate combinations for CT applications using the developed model. A sensitivity analysis is also conducted on underbalanced and CT drilling parameters on pressure drop and flow patterns.
Multiple Model Seismic and Production History Matching: A Case Study
Authors: Stephen K. D. , Soldo J. , MacBeth C. , Christie M.
Published: December 2007

Time-lapse (or 4D) seismic is increasingly being used as a qualitative description of reservoir behaviour for management and decision making purposes. When combined quantitatively with geological and flow modelling, as part of history matching, improved predictions of reservoir production can be obtained. Here, we apply a method of multiple model history matching based on simultaneous comparison of spatial data offered by seismic, as well as individual well production data.

Using a petro-elastic transform and suitable re-scaling, forward modelled simulations are converted into predictions of seismic impedance attributes and compared to observed data by calculation of a misfit. With a similar approach applied to dynamic well data, the total misfit is used to update model probabilities in a Bayesian framework. These are then used to guide the re-sampling of the parameter space, generating multiple models using the quasi-global stochastic Neighbourhood Algorithm (NA) method. This approach improves on gradient-based methods by avoiding entrapment in local minima and can be used to efficiently analyse uncertainty of the matched parameters.

We demonstrate the method by applying it to a UKCS turbidite reservoir, updating the operator's initial model, which had previously been history matched to dynamic well data by conventional methods. We consider a number of parameters to be uncertain. The reservoir's net to gross is initially updated to better match the RMS amplitudes of the observed seismic baseline survey. We match simultaneously for permeability, fault transmissibility multipliers and the petro-elastic transform parameters. Our results show a good match to the observed seismic and dynamic well data with significant improvement to the operator's base case.
Potential Non-Traditional Uses of By-Product E&P Produced Sulfur in Kazakhstan
Authors: Beall P. W. , Neff J. M.
Published: December 2007

Kazakhstan based oil & gas companies recover approximately 2,000 to 3,000 metric tons per day of elemental sulfur from their product streams (approximately 500 tons of elemental sulfur is recovered for every 100,000 barrels of extracted petroleum in Kazakhstan). The bulk of the sulfur is recovered by Tengizchevroil (TCO). In Europe and the United States recovered elemental sulfur is normally sold into the chemical and manufacturing market as a raw material for:phosphate fertilizer (50%)sulfuric acid, detergents, and other chemicalsmetal and fiber industriespaint manufacturerubber productspaperpharmaceuticals

By-product elemental sulfur can potentially be used as a binder replacement in petroleum asphalt and Portland concrete as sulfur modified asphalt and concrete to meet or exceed American Society for Testing and Materials (ASTM) and/or American Concrete Institute (ACI) standards.

Potential Applications for Sulfur Polymer Concrete & Sulfur Extended Asphalt

Improving the highway infrastructure using sulfur modified concrete and asphalt might be a steady outlet for locally produced elemental sulfur. The sulfur extended asphalt can extend current Kazakhstan asphalt production capabilities by upwards of fifty weight percent (25 volume percent).

Other potential outlets for Kazakhstan produced sulfur include:Sulfur polymer concrete slabs and blocks for constructionSulfur Polymer Stabilization Solidification for radioactive and mercury contaminated materials

Screening-level Ecological Assessment for Sulfur Modified Concrete and Asphalt

The environmental behavior of these sulfur-modified construction materials resembles that of conventional Portland cement concrete and hot mix paving asphalt, except for the possible release of sulfur to the environment.
Tertiary Oil Recovery With Microbial Biosurfactant Treatment of Low-Permeability Berea Sandstone Cores
Authors: Maudgalya S. , McInerney M. J. , Knapp R. M. , Nagle D. P. , Folmsbee M. J.
Published: December 2007

Experiments focused on tertiary oil recovery of waterflood residual oil using a bio-surfactant flooding process are reported in this paper. Significant quantities of water flood residual oil were recovered when very low concentration bio-surfactant solutions were flooded through 25-200 md Berea sandstone cores. The residual oil recovery ranged between 35% and 45% as surfactant concentrations varied from 35-41 ppm.

Cleaned and dried Berea sandstone cores, six inches long and one and half inches in diameter with an average porosity of 16.0 % were first saturated with 5.0% NaCl brine, then saturated with 340 API crude oil and finally waterflooded to near residual oil saturation. Thirty five to forty five percent of that residual oil was recovered when the cores were flooded with surfactant combined with a 0.001% by vol. co-surfactant alcohol and 1000 ppm of partially hydrolyzed polyacyalamide (PHPA) as mobility control polymer. The co-surfactant alcohol was added to reduce the effect of salinity.

The bio-surfactant concentrations reported are much lower than those previously reported in synthetic surfactant laboratory tests. The oil recovery in terms of bio-surfactant consumed is also substantially higher than previous surfactant tests. This tertiary recovery process may help improve oil recoveries from many marginal oil fields operating a waterflood that produce small amounts of oil at high water cuts or those that have been abandoned due to uneconomic operating costs but still contain significant amounts of oil.
Evaporative Clean-Up of Water-Blocks in Gas Wells
Authors: Mahadevan J. , Sharma M. M. , Yortsos Y. C.
Published: December 2007

The flow of a gas in to a wellbore in a production well can result in the evaporative cleanup of water blocks. This occurs primarily due to the expansion of gas resulting in additional water being evaporated in the near wellbore region. This study presents for the first time, equations and a model to calculate the rate at which the water block is removed in both fractured and unfractured gas wells.

It is shown that the removal of water by the expanding gas leaves behind a saturation profile that is qualitatively different for low and high permeability rocks. As a consequence the increase in gas relative permeability or the well productivity with time can vary substantially depending on the rock permeability and the well drawdown. The model allows us to compute the impact of evaporative cleaning on well productivity.

It is seen that high permeability rocks clean up significantly faster. It is also observed that unfractured wells may require a very long time to cleanup. Large pressure drawdowns as well as the use of more volatile fluids such as alcohols result in significantly faster cleanup. A distinctive feature of the study is that the model equations are formulated and solved completely without the assumption of skin factors for the damage zone. Thus the prediction of cleanup rates can be made more accurately.
Multilateral Horizontal Well Productivity
Authors: Yildiz T.
Published: December 2007

This paper presents experimental and theoretical investigations of multilateral/duallateral horizontal well performance in areally anisotropic reservoirs. The investigation is based on a 3D analytical solution. The analytical solution considers an arbitrary orientation of the multilaterals/duallaterals in horizontal plane.

Experimental study was conducted on an electrical analog apparatus. Experimental data was compared with the results from the analytical productivity model. Excellent agreement was obtained between the results.

The multilateral well model was also compared against a model presented in the literature and verified.
Training for the Future: Are Your Potential Liabilities Covered?
Authors: Roberts R.
Published: December 2007

Corporate liabilities in conjunction with training can be concerning for many Oil and Gas companies across the world. The regulatory aspect of training is very cumbersome and unique to the oil industry due to the complexity of work environments, time restraints and reduction in production hours. Numerous consultants, engineers and various workers throughout the Oil Field sites are performing safety meetings, yet are lacking in appropriate hours spent on environmental and safety compliance. Most companies have trained employees in some aspect although, regulatory compliance is not achieved due to the numerous O.S.H.A. standards and training competency mandated levels. The resolve to some of the concerns involve alternative learning styles such as computer based training, hands-on training and hired consultants to provide training.
Underground Gas Storage in Porous Media - Operating Experience with Bacteria on Gas Quality
Authors: Kleinitz W. , Böhling E.
Published: December 2007

The purpose of underground gas storage in porous media is to allow compensation for peak shaving in gas consumption. Especially during the winter months, the stored gas must then be supplied at full capacity for short periods. However, it must be ensured that the characteristic properties of the gas, such as the calorific value, the Wobbe index, etc., are not qualitatively impaired during the storage period. These values also include the concentration of H2S, which must remain below a specified limit of 5 mg/m³ (Vn).

During many years of operation with gas storage facilities, however, practical experience has shown that substantial technical efforts are necessary for observing this limiting value. Among the various possible causes, H2S can be generated as a result of dissimilatory sulphate reduction.

The activities of isolated SRB strains are discussed with respect to substrate utilisation (hydrate inhibitors), life conditions (temperature, pH value) and stimulation of storage wells.
Development of Low-Permeability Carbonate Reservoir by Use of Horizontal Wells in Mature South Umm Gudair Field in the Neutral Zone–A New Approach
Authors: Jha M. , Tran T. , Hagtvedt B. , Al-Haimer M. , Al-Harbi M.
Published: December 2007

The South Umm Gudair (SUG) oil field located in the Neutral zone between Kuwait and Saudi Arabia has produced since 1968 from an active water drive carbonate reservoir of Lower Cretaceous age. The lower zones are homogenous intervals of higher permeability which appear to be sufficiently swept by natural water drive over a period of time. The upper zones of the reservoir are more heterogeneous and have lower permeability in the range of 50-150 millidarcies. These upper zones are relatively thin and are bound by tighter intervals that act as effective barriers to the natural water drive system. Due to the presence of barriers and low permeability intervals, these zones have been poorly swept resulting in significant volumes of by-passed oil remaining in these parts of the reservoir.

The new approach of exploiting these reserves by drilling and completing 4 horizontal and 2 horizontal side track (HST) wells targeting the lower permeability portions of the reservoir in the SUG field since January 2004; have yielded considerable success in extracting significant incremental oil production with the added benefit of very low water cut. This success has led to field development plan to recover un-swept oil reserves from these low permeability zones. This paper summarizes the various aspects of field development plan taking into consideration geology, reservoir data and production data while highlighting the successes of the new horizontal and HST wells in the low permeability reservoir portions of the SUG field.
Detailed in Situ Stress Measurements for Qualifying the Safety of Underground Gas Storage Overburden
Authors: Fourmaintraux D. M. , Bois A. -P. , Le Goff C. , Cantini S.
Published: December 2007

Operations performed on one underground natural gas storage facility detected gas traces in its overburden. This led the safety management to request that the sealing of the overburden of this storage facility as well as of a sister facility be checked and re-qualified.

Gas is injected in the top of two gentle tertiary anticlines within a regional aquiferous sandy layer overlaid by a thick molassic shaly overburden. The main risk for leakage is the risk of "hydro-fracturing the cap rock", which is controlled by the value of the minimum horizontal in situ stress.

This paper focuses on data acquisition of 37 mini-frac tests and 3 ELOTs. These tests allowed drawing a representative profile of the minimum horizontal stress between 150 m to 525 m deep, and also to evaluate its direction.

These data were used as input to numerical simulations that showed that gas injection and withdrawal result in in-phase displacing the overburden up and down and that no damage mechanical damage occurs.
Hydraulic Jet Pumps Prove Ideally Suited for Remote Canadian Oil Field
Authors: Anderson J. , Freeman R. , Pugh T.
Published: December 2007

With 150 Million Barrels of recoverable reserves, the Nexen Hay River Bluesky oil pool is among the largest oil discoveries in Western Canada in the past two decades. Initial pilot production testing lead to the conclusions that, in order to produce the field in its most economical fashion, the following would be needed: Triple lateral horizontal producing wellsIn field horizontal water injection/water disposal wells for pressure maintenanceArtificial Lift from the outset

Further complicating production of the Hay Pool, which is located in a remote area of North-Eastern British Columbia, was the fact that road access would be limited to 4 months of the year because any road through the muskeg would need to be "frozen in" prior to use. It was therefore extremely important to the economic viability of the project that whatever means of artificial lift were chosen should be highly reliable and require minimal maintenance. The method chosen, apart from being reliable and safe, would also need to be capable of lifting large volumes of fluid with a significant pressure drawdown. In addition it would need to be able to operate successfully in the extreme well deviations common in the "build" sections of the development wells.

This paper will review the development of the Bluesky oil pool and present the case for the choice of Jet Pumps for artificial lift. The authors will go on to detail the performance of the Jet Pump system installed in the field that has met or exceeded all performance expectations.
Technical Improvements in Mill Profile Design and Cutting Structures: Case Histories and Developments
Authors: Voden G. S. , Pfannenstiel G. , Matthews R.
Published: December 2007

The ever increasing operator demands and objectives to mill fast and efficient windows has led to the development of innovative milling technology. New lead mill profiles and cutting structures have replaced old crushed carbide technology.The new design utilizes inserts brazed into pockets machined in the mill head. Mills dressed with the new cutting structure are able to effectively mill a casing window and drill formation rat hole in less time than it took with the welded-on crushed carbide technology.

With this new design, operators are now afforded an option. In medium to hard formations, the new cutting structure can be used to mill the window and drill rat hole in one trip. While sidetracking in formations with high compressive strengths, Polycrystalline Diamond Compact (PDC) inserts can be utilized. The use of the new cutting structure in a one trip sidetrack system can result in substantial cost savings, improved milling reliability and a higher quality window.

The combination of new cutting elements and mill profile has proved to be economically sound allowing for consistency of product manufacturing and has eliminated the potential variances inherent in the welding processes. The system design and cutting structure reduces torsional resistance providing for smoother in-gauged milled windows in one trip.

This paper updates an earlier paper with the concepts of using the new cutting structure and presents the new technology and recent case histories of four sidetrack operations.
Determination of Multilayer Reservoir Inflow Profiles Using Pulsed Neutron Logs
Authors: Poe B. D. , Butsch R. J. , England K. W.
Published: December 2007

This paper addresses the development and validation of a production logging analysis methodology and associated formation inflow interpretation model for wells that have their production tubing string setting depth below the top of at least the shallowest completed interval in the well.This type of completion technique is commonly utilized in wells that produce formation liquids and in which the tubing is lowered in the well below the top of the shallowest(and possibly additional deeper) completed interval(s) in order to assist in unloading the well of the produced liquids.When this is done, conventional production logging tools and techniques can not be used to measure the inflow profile of the completed intervals that are shallower than the tubing setting depth in the well without raising the tubing above the shallowest completed interval, which can alter the inflow profile of the well.

This paper specifically considers the development of a reliable means of performing an equivalent inflow performance analysis, analogous to that which would be obtained with conventional production logging analyses if those inflow profile evaluation techniques could be used in wells with this type of completion.The liquid holdup of the multiphase flow in the well is determined from the Inelastic Ratio measurements of a Pulsed Neutron log and the annular water velocity is directly obtained from the analysis of water flow measurements in the annulus of the well.
Preventing Asphaltene Deposition in Oil Reservoirs by Early Water Injection
Authors: Wang S. , Civan F.
Published: December 2007

A comprehensive modeling and simulation of asphaltene precipitation and deposition in petroleum reservoirs is carried out. The effects of the asphaltene deposition on reservoir properties, and the productivity of the vertical and horizontal wells during primary oil recovery are demonstrated. An early water-injection development scheme for suppressing asphaltene deposition is proposed and its feasibility is investigated by means of simulation. The performance of the early water-injection development scheme is compared with the direct depletion development scheme. The results indicate that the early water-injection not only increases the oil recovery significantly but also extends the economic production life of the reservoir considerably.
A Review of Downhole Separation Technology
Authors: Ogunsina O. O. , Wiggins M. L.
Published: December 2007

In recent years, a technique of separating water downhole to reduce the volume of produced water and decrease the chance of surface pollution has been developed. It is called downhole oil-water separation (DOWS) technology. This technique allows water to be separated in the wellbore and injected into a suitable injection zone downhole while oil with traces of water is produced to the surface.

Subsequent to the introduction of the DOWS technology to the oil industry in the 1990's, several trial applications have been undertaken to test the technology. These trials allowed significant information to be collected on the feasibility of the DOWS technology. Through the joint efforts of Argonne National Laboratory, CH2M-Hill, and the Nebraska Oil and Gas Conservation Commission, a comprehensive technical report was issued in January 1999 discussing this technology. Additional reports on trial applications and feasibility studies have been presented by various study groups.

This paper reviews the status of and issues surrounding the application of downhole separation technology. This review summarizes the various papers and reports dealing with DOWS technology and its application in the oil and gas industry. This technology has the potential to provide significant reductions in produced water as the technology is adopted by the industry. It can also reduce produced water handling costs and increase oil and gas production in the right application. The wide-spread adoption of DOWS technology is dependent on improving the understanding of the process and its applications throughout the oil and gas industry.
Friction Pressure Correlations for Newtonian and Non-Newtonian Fluids in Concentric Annuli
Authors: Singhal N. , Shah S. N. , Jain S.
Published: December 2007

Flow through annulus is frequent in drilling and work-over operations. Annular flow is also utilized in some fracturing treatments. In all these applications, Newtonian and non-Newtonian fluids are widely used. Therefore the knowledge of annular flow performance of these fluids becomes important for planning and design of well-bore hydraulics. Existing knowledge about the behavior of non-Newtonian fluids in annulus is very limited due to their complex behaviour. A range of correlations is available in the literature for both Newtonian and non-Newtonian fluids in laminar and turbulent flow regime. Selection of the appropriate correlation for the desired fluid and flow regime is very important for the accurate determination of friction losses.

Experimental and simulation study has been undertaken to investigate the flow behavior and friction pressure losses of Newtonian and non-Newtonian fluids in concentric annuli. Computational Fluid Dynamics (CFD) has been used along with limited experimentation on a field-scale set up to validate the simulation results. The fluids investigated are water and frequently used concentrations of guar and Xanthan fluids. CFD simulations have been performed for different annular dimensions in flow range encompassing both the laminar and turbulent flow regimes. The annular dimensions used in the simulations cover the range used in the industry. The frictional losses of non-Newtonian fluids exhibiting drag-reducing characteristics have been investigated through experiments.

Based on the comparison with simulation results recommendations are made to use the appropriate correlations for Newtonian and non-Newtonian fluids in the laminar and turbulent flow regime.Improved correlations are proposed to determine frictional losses of non-Newtonian fluids exhibiting drag-reducing characteristics. These correlations are based on experimental data gathered for a wide range of concentrations of guar and Xanthan fluids. The recommendations made along with the correlations presented in this study will greatly improve the accuracy of determining friction pressure losses in concentric annuli.
Locating Remaining Oil in a Mature Waterflood: A Case History
Authors: Calogero D. B. , Stevens G. A. , Hall R.
Published: December 2007

The Walnut Bend Field was discovered in 1938 and consists of over 70 Pennsylvanian channel sands draped over an elongated, anticlineal structure approximately 3 miles long and 1.5 miles wide. The main body of the field had produced over 99 MMBO by 1999 when a field revitilization project was initiated. This project was a success, both technically and commercially. The success of this program was due in large part on a new volumetric-balancing technology that provided accurate present day oil in place maps. Some of the highlights of this project are: 80% accurate prediciaon rate of current day hydrocarbons1,080,000 bbls of reserves added35% increase in productionComprehensive multi-year revitalization plan.
Using Chemical Tracers and Production Analysis for Early-Time Assessment of Stimulation Effectiveness and Reservoir Quality for Barnett Shale Completions
Authors: Townsend A. , Anderson K. , Gunderson D.
Published: December 2007

For every well drilled, there is a performance expectation.At a minimum, there is a forecasted Pi, initial production rate, and time to payout. When the well's production does not meet expectations, it is common to wonder whether the problem is the reservoir, the completion, or the wellbore.Answering these questions quickly, accurately, and inexpensively is difficult enough with single-zone completions; however, it has been virtually impossible for wells with commingled production.Historically, even simple wells defied rigorous investigation without costly and time-consuming pressure buildup analysis.To determine the critical characteristics that dictate a well's performance, a non-intrusive method is necessary.When employed with robust, post frac, drawdown production analysis, the Chemical tracer technology unlocks the keys to understanding important reservoir parameters in single and multiple zone completions.

Several Barnett Shale well case histories will be presented to demonstrate the application of this methodology.These case histories illustrate the value of being able to allocate production to individual zones in Barnett Shale wells with commingled production.
Environmental Impact of Oil and Gas Operation: A Case Study of Drilling-Mud Disposal in Niger Delta, Nigeria
Authors: Ndufor P. N. , Idehen K. I.
Published: December 2007

The paper report is the technical assessment on the environmental impact of burried drilling chemicals, which were later exhumed, the study parameters includes the physical, chemical, biological and socio-economic status of the dump site of chemical waste, recommendation cum mitigative measures was proferred.
Contact Pressure Threshold: An Important New Aspect of Casing Wear
Authors: Hall Russell W. , Malloy Kenneth P.
Published: December 2007

Drilled wellbores have evolved from nearly vertical, shallow holes to tortuous, deep, directionally drilled wells. As wellbore geometries have increased in complexity, so has the potential of damage resulting from casing wear. It is not unusual to routinely install ditch magnets in the returned drilling fluid circuit to catch the iron filings created by tool joint wear against the casing or riser interior wall.

While most "straight" holes attempt to control inclination, azimuth control is often times neglected, potentially creating a tortuous path. In directionally drilled holes, including horizontal and multi-lateral wells, the drill string tension holds the rotating tool joints against the inner wall of the casing for extended periods. This results in the generation of crescent shaped wear grooves (key seating) in the inner wall of the casing, often dangerously weakening casing or riser strings making them more susceptible to burst or collapse.

Some investigators have sought to quantify this damage process. Computer models describe, measure, and predict damage from casing or riser wear. From these on-going studies, advances in technology continue to minimize casing and riser wear.
A Two-Phase IPR for Horizontal Oil Wells
Authors: Wiggins M. L. , Wang H.-S.
Published: December 2007

This paper investigates the rate-pressure behavior of a horizontal oil well with a fully penetrating wellbore producing during the boundary dominated flow regime. Based on linear regression analysis of simulator results, two empirical inflow performance relationships (IPRs) are developed to estimate well performance. A future performance relationship is also developed to allow estimates of future rate-pressure behavior from current test information. The IPR relationships are compared to other horizontal IPRs available in the literature and yield reasonable estimates of well behavior over a wide range of operating conditions.
Improved Treatment Methodologies for Removing Low Concentrations of H2S in South Texas Natural Gas Systems
Authors: Lillard D. M. , Macias J. M.
Published: December 2007

Removal of hydrogen sulfide from natural gas is a primary concern for many producers. Many natural gas systems throughout the South Texas area have H2S concentrations that range from less than 10 ppm to more than 1000 ppm. While amine units are usually efficient at removing H2S cost-effectively, the high capital cost has encouraged the development of other treatment methodologies for the removal of low to moderate quantities of H2S from natural gas. One such method is the injection of liquid chemical scavengers directly into the gas stream. The chemical scavenger reacts with the H2S and forms a product that is removed from the gas by separation equipment, such as a scrubber.

Although the chemistries of the scavenger reactions are fairly well known, the efficiency and therefore the cost-effectiveness of removing H2S by this method is highly dependent on system conditions and architecture. Many parameters impact the efficiency of liquid H2S scavenger application. Important factors include mixing, a function of several parameters such as gas velocity and injection method, and retention time, which is the time available at a specific set of conditions to achieve maximum scavenger efficiency. Based on these and other factors, a field study was undertaken to evaluate the effects of system conditions, architecture modifications, and of specialized equipment types on improving the efficiency of H2S removal. This paper will present field data and describe the mass balance efficiencies of several types of scavenger applications including injection into existing systems, the use of retention treating loops, and bubble towers for the removal of H2S.

The use of mass balance calculations during the project allowed for careful assessment of scavenger efficiencies in a variety of conditions and treatment scenarios. Mass balance is a useful tool when liquid scavenger testing includes several formulations of varying concentrations. The results of the field evaluation provided data that led to a better understanding of liquid scavenger usage and applications limits. The improved understanding of treatment envelopes allows field users to more efficiently identify candidate scavenger processes and make more informed decisions on process selection for removal of H2S from natural gas streams.
Utilizing Flowing Pressure-Transient and Mass-Balance Analysis of SENM Morrow Producers To Calibrate 3D Hydraulic-Fracture Modeling – A Case History
Authors: Walser D. W.
Published: December 2007

Sizing of hydraulic fracturing treatments in the Southeastern New Mexico (SENM) Morrow has historically relied on a trial-and error process whereby a three-dimensional fracturing model was built and run with simple gamma ray and compensated neutron density logs.Stress tables have been built utilizing over-simplified correlations involving conversions from gamma ray readings and effective porosity.The resulting simulated fracture-half lengths have been utilized in NPV (Net Present Value) optimizations to arrive at a final sizing decision.

Unfortunately, this process relies on the assumption that the initial modeling generates a propped fracture geometry simulation that is realistic.Past efforts to calibrate the 3-D models in the area focused on scattered attempts to gather sonic data that could be converted to stress differentials, and the use of conventional pressure buildups before and after the treatment.While the measurement of sonic properties during open-hole logging operations assisted somewhat in calculating relative stress differentials, its application was sporadic at best, and there was no way to check the results. Pre and post-stimulation pressure buildups required shutting the well in for a period of time and subsequently risking potential deceleration of reserve recovery.

A study of a variety of existing Morrow producers was undertaken to determine whether or not flowing pressure transient analysis of existing properties could be utilized to "calibrate" three-dimensional fracturing models, so that future projects would better reflect fracture geometries that were more realistic than current practice.

Results of the study are presented, and a practical, user-friendly model is demonstrated whereby flowing transient analysis may be utilized to adjust three-dimensional fracturing simulations as appropriate for optimizing stimulation NPV.
A Review of Horizontal-Wellbore Pressure Equations
Authors: Anklam E. G. , Wiggins M. L.
Published: December 2007

The objective of this paper is to review the current methods of determining how the effects of wellbore hydraulics are incorporated into the evaluation of the productivity of a horizontal well.Wellbore hydraulics includes the effects of friction, acceleration, gravity, and fluid influx.Knowledge of the pressure distribution within the horizontal wellbore is important to more accurately determine the performance of the horizontal well and aides in the design of the well profile, completion, and stimulation.
Wave Equation Simulation of Fluid Pound and Gas Interference
Authors: Yavuz F. , Lea J. F. , Garg D. , Oetama T. , Cox J. , Nickens H.
Published: December 2007

Using adiabatic compression of gas in the pump, a model is shown that can be used to calculate the down-hole pump dynamometer card for various degrees of pump fill of liquids and gas at various degrees of pressure. The load release portion of the card is emphasized. It is shown how the lower pressure gas in the pump promotes what is commonly termed fluid pound or slap and higher pressure gas in the pump promotes what is termed gas interference.

The equations that are needed to model these effects for inclusion into wave equation pump models are presented and example calculated pump cards are shown, calculated from wave equation simulations. Since even with so-called fluid pound, gas is first compressed before the plunger encounters the mostly incompressible fluid in the pump, the traveling valve always encounters compressed gas sufficient to open the valve before the plunger "hits" the fluid. This is true as long as gas is in the barrel when incomplete fluid fill occurs. Given this fact, the time step in wave equation solution is examined as the load release in the so called "fluid pound" can happen over a very short time and longer time steps in the wave equation simulation could mask forces from short term forces.

The effects of rapid load release on forces in the rods are studied vs. what the forces might be due to the commonly supposed forces from impact with the fluid when "fluid pound" is modeled. Other parameters such as pump fillage, intake pressure and sinker bars are examined for their effects on calculated rod compression
A Coupled Model for Analyzing Transient Pressure Behavior of Horizontal Drainholes
Authors: Ogunsanya B. O. , Oetama T. P. , Lea J. F. , Heinze L. R. , Adisoemarta P. S.
Published: December 2007

Conventional horizontal well transient response models are generally based on the line source approximation of the partially penetrating vertical fracture solution1. These models have three major limitations: (i) wellbore pressure is computed at a finite radius outside the source; it is impossible to compute wellbore pressure within the source, (ii) it is difficult to conduct a realistic comparison between horizontal well and vertical fracture productivities, because wellbore pressures are not computed at the same point, and (iii) the line source approximation may not be adequate for reservoirs with thin pay zones. This work attempts to overcome these limitations by developing a more flexible analytical solution using the solid bar approximation. A technique that permits the conversion of the pressure response of any horizontal well system into a physically equivalent vertical fracture response is also presented.

A new type curve solution is developed for a horizontal well producing from a solid bar source in an infinite-acting reservoir by means of Newman's product solution2. Analysis of computed wellbore pressures reveals that error ranging from 5 to 20% was introduced by the line source assumption depending on the value of dimensionless radius (rwD). Computations show that for rwD ≤ 10-4 the transient response of a horizontal well is identical to that of a partially penetrating vertical fracture system, and for rwD > 0.01 the transient response of a horizontal well is indistinguishable from that of a horizontal fracture system. Type-curve plots for the ranges 0.01 ≤ dimensionless length (LD) ≤ 10, and 10-4 ≤ rwD ≤ 1.0 are presented.

A dimensionless rate function (β -function) is introduced to convert the transient-response of a horizontal well into an equivalent vertical fracture response. A step-wise algorithm for the computation of β -function is developed using Duhamel's principle. This provides an easier way of representing horizontal wells in numerical reservoir simulation without the rigor of employing complex formulations for the computation of effective well block radius.