bluuebunny/crossref_metadata_2025 huggingface dataset:
MacKay River SAGD Project Benefits From New Slant Rig Design
Authors: Miller H. , Osmak G. M.
Published: December 2007

Drilling oil sands in the first phase of a steam-assisted, gravity-drilling (SAGD) commercial project in northern Alberta, Canada, presented numerous challenges. The oil sands are too deep for surface mining and too shallow for conventional horizontal drilling. In addition, over-warming these bituminous sands can result in significant wellbore problems.

While conventional slant rig technology could effectively reach the oil sands, the economics of moving the rig between project well sites was not favorable. To improve economics, a new centralized rig design was required that allowed auxiliary drilling equipment to remain stationary while the rig and tubulars moved between wells. A central mud system with specialized cooling and solids control equipment was required to address over-warming of the bituminous sands. The final design also included computer-assisted rig moves, a differential pressure torque monitoring system and floor winches configured to apply pull-down force.

This paper examines the planning process that involved close coordination between the operator and the drilling contractor, and the equipment used in the new rig design. The paper also reviews the drilling of 25 well pairs that allowed completion of the project under budget and four months ahead of schedule.
Mixing Cement by Solids Fraction Instead of Density
Authors: Vigneaux Pierre G , Rondeau Joel , Pathak Rakesh
Published: December 2007

While mixing cement on the fly any density error made may induce large changes in critical slurry properties. Therefore controlling density during a cementing job is known to be one of the key factors to the success of the operation. This led service companies to develop process controlled mixing systems. These equipments work reasonably well when the density of the dry powder – the cement blend – differs significantly from that of the mix water, which is quite often the case.

Blends with engineered particle size distribution have allowed designing cement systems with high performances nearly independently of their density. Recently this technology was upgraded to provide comparable physical properties at slurry density similar to that of water. These new cement blends now have a density that can be equal to that of the mix water. In this case, it is clear that the mixing process cannot be monitored or controlled by measuring the density of the mixed fluid since the mix water, the cement blend and therefore the mixed slurry all exhibit the same density.

To overcome this problem, a new quality control principle based on solids fraction measurement was developed. The first part of this article presents the basic principles of the new device as well as their implementation on existing field equipments. The second part discusses the key advantages of controlling solids fraction and proposes to make it a universal quality control parameter for not only ultra-lightweight high performance slurries, but also for conventional systems be they lightweight or heavyweight. The benefits associated to this new technology are illustrated through the analysis of various cementing jobs while mixing slurries as light as water or at a much higher density.
Use of Vapor Desorption Data to Characterize High Capillary Pressures in a Basin-Centered Gas Accumulation with Ultra-Low Connate Water Saturations
Authors: Newsham K. E. , Rushing J. A. , Lasswell P. M.
Published: December 2007

This paper presents results of a laboratory study of capillary pressure characteristics of core samples from the Bossier sands in the Mimms Creek Field located in Freestone Co., TX. The Bossier tight gas sand play is believed to be part of a basin-centered gas system (BCGS) in the East Texas Basin. Similar to other BCGSs, the Bossier sands are sometimes characterized by an abnormally high capillary pressure profile associated with an ultra-low connate water saturation distribution. We use a vapor desorption technique to measure capillary pressures as high as 10,000 psi and corresponding to water saturations as low as 1%. We also compare capillary pressures measured with a centrifuge and demonstrate our inability to fully define the pressure-saturation range observed in the Bossier sands using a centrifuge.
Reliable Simulation Model Permeability Arrays By Integration of Core, Test, and Log-Derived Permeability Data
Authors: Ghedan Shawket G. , Boyd Douglas A. , Thiebot Bertrand M.
Published: December 2007

The generation of permeability models that best describe the reservoir heterogeneity and its flow dynamics is a difficult objective to achieve. This paper addresses the multi-step procedure followed and the various analytical techniques utilized to integrate different types of permeability data to generate multiple realizations of permeability, which were fed and tested in a dynamic reservoir simulation model for initialization and history matching.

Due to the limited availability of core permeability data and lack of vertical resolution in test permeability data, most modelers rely on statistically log derived permeability predictors to generate permeability models. This paper discusses the design, merits and drawbacks associated with three permeability predictors included in the static geological model of a major carbonate reservoir in offshore Abu Dhabi, along with the rock-typing scheme utilized.

Four analysis techniques are utilized to screen and choose the right permeability predictor for the right sub reservoir or layer of the field. These are merged to generate the first realization of permeability for the simulation model after upscaling.

Test KH conditioned to core KH is taken as a reference in the screening and testing process. The conditioning process is performed at the wells levels to add the core permeability vertical resolution to test permeability data and produce a new log for that matter. This new log is utilized to produce two additional permeability realizations for the simulation model by either conditioning at the wells level followed by modeling and upscaling, or conditioning at the geological model after modeling followed by upscaling.

The initialization of the simulation model is completed with each of the three permeability and rock type realizations. The fluids in place are very close and model is equilibrated. The simulation model performance of the initial history matching runs was found to be very close to the field observed performance for a very complicated and heterogeneous carbonate reservoir. In our case, a combination of the conditioned permeability models are found to be best for achieving a quality history matched simulation model.
Innovative Business Partnership Produces Effective Water Conformance Treatments
Authors: Mitchell W. , Martin A. N. , Stemberger D. , Thayanukulvat P.
Published: December 2007

Historically, water conformance treatments have often proved to be problematic and unreliable. Often, expectations are unrealistic and candidates poor. In addition, wells are treated individually and subsequent unrepresentative results are taken to be the norm. Products or processes that are genuinely effective under the right conditions are often written off as failures, due to ineffective placement or use on unsuitable candidates. However, this does not have to be the case. With proper candidate identification, correct treatment selection and effective treatment placement, water conformance treatments can be placed with a high degree of success.

This paper will describe the processes necessary for this to be achieved. These fall into three main stages – candidate selection, treatment selection and treatment execution. Each one of these stages is critical. For the process to work, the right treatment has to be placed at the right point, in the right well. The paper will also detail the care taken in the candidate selection process and illustrate just how critical this is. It will go on to discuss the need for good treatment design and the effective placement of the system selected. The paper will conclude by providing case histories from the offshore Java Sea area, to illustrate just how effective this process can be.
Enhanced Gas Recovery (EGR) with Carbon Dioxide Sequestration: A Simulation Study of Effects of Injection Strategy and Operational Parameters
Authors: Jikich Sinisha A. , Smith Duane H. , Sams W. Neal , Bromhal Grant S.
Published: December 2007

Injection of carbon dioxide into a natural gas reservoir is a promising technology for reducing anthropogenic gas emissions and increasing ultimate recovery of natural gas. Computer simulation is an important, inexpensive tool for designing pilot projects and predicting optimal tradeoffs between maximum methane production and maximum sequestration.

To investigate the amount of carbon dioxide sequestered and the effect of carbon dioxide injection on gas recovery, different injection strategies were used for a thin, shaly sandstone reservoir situated in Northern West Virginia. Two injection scenarios were studied: (1) simultaneous CO2 injection and methane recovery from the very beginning of the project, and (2) primary production of natural gas to the economic limit, followed by injection of carbon dioxide for secondary gas recovery. Horizontal injectors were used to increase injectivity. A 160-acre inverted 5-spot well pattern was studied for a pilot test.

The simulation results show that the highest methane recovery was obtained when the reservoir was produced under primary recovery until the economic limit, followed by CO2 injection. The maximum amount of incremental gas recovery was less than 10% of the original gas in place (OGIP). Lower recovery factors for methane were obtained in the case when CO2 injection was injected early. However, the early CO2 injection accelerated methane recovery and improved CO2 retention in the reservoir. The simulations also showed that there was an optimum length for the horizontal injectors to sequester the maximum amount of CO2.

By varying operational parameters such as time of primary production, injector length, injection pressure, injection timing, and production well pressure we can evaluate different production schemes to determine an optimum recovery of methane vs. CO2 sequestration. The findings of this study can be useful for finding tradeoffs between methane production and CO2 sequestration.
Decision and Risk Analysis Tools for the Oil and Gas Industry
Authors: Virine Lev , Rapley Lisa
Published: December 2007

The concept of decision and risk analysis for economic and engineering applications has become widely accepted in the petroleum industry. However, the actual use of decision and risk analysis tools remains limited, due mostly to complexity of these tools. Moreover, the professional use of these tools requires advanced knowledge of decision and risk analysis theory. The solution is to integrate decision and risk analysis tools into petroleum economic and engineering applications using developer's kits or toolsets. Advanced visualization techniques should be applied to provide the visual aids to input data with uncertainties and simplify the analysis of the results.
Surfactant Dewatering of Production and Gas Storage Wells
Authors: Ramachandran Sunder , Bigler John , Orta David
Published: December 2007

Surfactant dewatering of gas wells is a method best used in an operating envelope determined by existing gas flow rates, well bore inner diameters, pressures and temperatures. Baker Petrolite has designed a computer model to determine this operating envelope. The methodology can help delay costly mechanical dewatering methods yet still maintain production in the field. Case studies for both production and gas storage wells will be discussed.
The Importance in Developing a Surveillance Logging Quality Assurance and Quality Control Plan
Authors: Newman Mark A.
Published: December 2007

A quality assurance and quality control (QA/QC) plan is important to the success of a surveillance logging program. A QA/QC Plan for a surveillance logging program can provide adequate and accurate information in assessing the level of pipe defects reported from casing inspection logs and can be used to record possible trends regarding individual casing inspection tools1. Measurements taken from pulled well casing can be used to enhance the analysis of general corrosion in areas of large-diameter pits. Over time the accuracy in estimating depth of penetration in large-diameter corrosion pits can be improved.
Characterization of a Heterogeneous Reservoir in West Virginia
Authors: Aminian K. , Ameri S. , Bilgesu H. I. , Alla V. , Mustafa R.
Published: December 2007

The production performance of a reservoir is invariably influenced by the degree of heterogeneity present. Therefore, production performance of a heterogeneous reservoir cannot be realistically predicted without accurate reservoir characterization. In this study, a systematic and synergistic approach has been employed to integrate and interpret various geological and engineering data that are obtained at different scales to characterize a complex oil reservoir in West Virginia. The lack of detailed data significantly hampered the reservoir characterization efforts. However, innovative approaches that combined statistical and artificial intelligence techniques were successfully developed and utilized to predict the missing information. These approaches help reconcile stratigraphy, structural, and petrographic data with well log data, core analysis, and production data. The results were utilized to develop a model of the reservoir and to identify the flow units. The attributes of the flow units were quantified from well log data with help of Artificial Neural Networks (ANN). An innovative approach for training and testing of the ANN was developed which provided consistent and reliable predictions. Primary and secondary production data have been utilized to evaluate and modify the model. The flow unit model substantially improved the simulation of the secondary recovery performance. The simulation results confirmed the presence of heterogeneities which have had profound impact on the performance of the reservoir. The methodology presented in this paper can serve as a guideline for the characterization of reservoirs with limited data.
The Colfax Field Rose Run: A Reservoir Study
Authors: Freeman D. C. , Blomberg J. R. , Tardivo J. J. , Knobloch T. S. , James J. J.
Published: December 2007

A reservoir study was undertaken to evaluate methods for depletion of the Rose Run formation located in the Colfax Field, Fairfield County, Ohio. The original oil-in-place and the drainage area affected by the existing wells were determined. Per well drainage areas ranged from 0.5-22.3 acres, all significantly less than the state-prescribed 40-acre spacing for wells producing from depths greater than 4000 ft. Depletion from existing wells, new drills, a horizontal well, and waterflooding was subsequently examined, primarily through the use of black oil reservoir simulation.
Comparing Fracture Simulation Design to Radioactive Tracer Field Results: A Case History
Authors: Silber Richard , Martin Jason , Willis Stan , Kozera Greg
Published: December 2007

This paper highlights the value of post-fracture tracer analysis as an evaluation tool to aid in fracture design. A fracture design can be evaluated and compared to actual field results. When the results of this fracture design analysis are then compared to tracer analysis and to predicted and actual deliverability, fracture design can be improved and optimized. To verify this procedure, five wells were chosen for a case study.

The chosen gas storage reservoir had two active pay zones separated by 14-30 ft. Radioactive tracers were run in the treatments of five gas storage wells. Wells were then logged to determine the location of the tracers and determine whether both zones were effectively stimulated. In addition to determining whether zones were effectively stimulated, determining fracture height and comparing measured to the design fracture height was possible.

All of the wells were flow tested before stimulation, and potential deliverability increase was predicted. Post-stimulation flow potential was estimated by the choke flowback results and compared to predicted results. (Multi-point flow tests will be conducted after one year of storage activity to determine actual results.) Flowback results indicate good correlation between fracture design predictions and actual field results.
Development of a Correlation for Estimating Gelation in Porous Media Using Bottle Test Measurements
Authors: Awang Mariyamni , Seng Goh Meng
Published: December 2007

The bottle test method that is currently used to estimate gelation only provides a qualitative description and also does not necessarily reflect what happens in a porous media. This paper aims to show a relationship between the permeability of a porous medium that has been injected with a pre gel polymer and the gelling state given by a bottle test. In this way a better estimation of the gel strength in the reservoir can be made.
EOR: Past, Present and What the Next 25 Years May Bring
Authors: Stosur George J.
Published: December 2007

The paper presents an analysis of worldwide EOR activities and trends for the mid-term future. The focus of the paper is on EOR production levels and the corresponding number of projects within each major EOR technology group: thermal, gas flooding, chemical and other methods.

Most EOR activities are in North America where the conventional oil production decline is now well established and EOR is one of a few remaining options for additional oil production. In the United States, the unfavorable economic climate of the late 1980’s caused the number of new EOR projects to decline rapidly, followed by the corresponding leveling of oil production and even a modest EOR production decline in 2002.

Thermal recovery continues to provide the largest, although it is declining fraction of EOR production. In the long-term, thermal recovery methods may play an increasingly important role in the recovery of the huge heavy oil and tar sands resources. Gas flooding continues to gain momentum and shows promise for further gains. Chemical flooding projects suffered from declining interest and negligible production rate. Fluid diversion via permeability modification control offers considerable near-term potential.

It is likely that EOR-produced oil in the United States has already reached its peak level and that it will increase above the current production rates only at substantially higher and stable oil prices. World’s EOR production peak is likely to occur 30–35 years after the onset of global oil production decline, or in mid 2060’s.
Application of Artificial Intelligence to Characterize Naturally Fractured Reservoirs
Authors: El Ouahed A. Kouider , Tiab Djebbar , Mazouzi Amine , Jokhio Sarfraz A.
Published: December 2007

In highly heterogeneous reservoirs classical characterization methods often fail to detect the location and orientation of the fractures. Recent applications of Artificial Intelligence to the area of reservoir characterization have made this challenge a possible practice. Such practices consist of seeking the complex relationship between the fracture index and some geological and geomechanical drivers (Facies, porosity, permeability, bed thickness, proximity to faults, slopes and curvatures of the structure) in order to obtain a fracture intensity map using Fuzzy Logic and Neural Network.

This paper shows the successful application of Artificial Intelligence tools such as Artificial Neural Network and Fuzzy Logic to characterize naturally fractured reservoirs. A 2D fracture intensity map and fracture network map in a large block from Hassi Messaoud field have been developed using Artificial Neural Network and Fuzzy Logic.

This was achieved by first building the geological model of the permeability, porosity and shale volume using stochastic conditional simulation. Then by applying some geomechanical concepts first and second structure directional derivatives, distance to the nearest fault, and bed thickness were calculated throughout the entire area of interest. Two methods were then used to select the appropriate fracture intensity index. In first method well performance was used as a fracture index. In the second method, which consists of a new proposed approach, a Fuzzy Inference System (FIS) was built. With such system static to dynamic data was coupled to reduce the uncertainty and resulted in a more reliable Fracture Index. The different geological and geomechanical drivers were ranked with the corresponding fracture index for both methods using a Fuzzy Ranking algorithm. Only much important data were selected to be mapped with the appropriate fracture index using a feed forward Back Propagation Neural Network (BPNN). The neural network was then used to obtain a fracture intensity maps throughout the entire area of interest. A mathematical model based on "the weighting method" was then applied to obtain fracture network maps, which resulted in a deep insight about the major fracture trends.

The obtained maps were compared in the end and the results show that the proposed approach is a feasible methodology to map the fracture network.
Estimation of Surface Tension for Two Immiscible Fluids Using Lattice-Gas Automata
Authors: Kristanto Dedy , Awang Mariyamni
Published: December 2007

Surface tension is one of the important properties in enhanced oil recovery, particularly for gas-liquid displacement in porous media and separation process. It acts to keep interfaces of two immiscible fluids smooth, where two or more curved interfaces create pressure differences. The estimation and measurement of surface tension currently are made by capillary rise such as the ring method and the pendant drop method. In this paper, the lattice-gas automata method is being explored to be used in estimating the surface tension between two immiscible fluids in a porous medium. The main idea of immiscible lattice-gas model in this paper was the introduction of two species of particles (red for gas and blue for oil) to represent two immiscible fluids. The great advantage of the model was that interfaces and the interfacial dynamics were generated spontaneously. The surface tension was estimated by the Laplace’s equation and ranged between 0.00585 –0.00603. In general, simulation results are in good quantitative estimation and this simulation also allow us to model liquid-liquid or gas-liquid interactions. The aim was to see the suitability of lattice-gas automata in representing two immiscible fluids of oil and gas.
How to Fracture More Than 30 Zones in a Well in One Day and Used in a Large Scale
Authors: Demin Wang , He Liu , Yan Wang , Gang Wang
Published: December 2007

This paper introduces a method to fracture more than 30 zones in a single well per day and also how to fracture low permeability zones when the impermeable barrier(s) to high permeability and high water cut zones are only about 0.5 m thick and not create channels in the cement sheathe.

The above methods are used in a large scale in Daqing Oil Field (about 1,000 wells per year since 1980). The results are quite good, cumulative incremental oil production by these fracturing methods is about 60 million tons; the fracturing costs per ton of incremental oil is about $ 6.
Massive Hydraulic Fracturing – A Case History in Western Siberia, Russia
Authors: Nor-Azlan N. , Sanchez A. I. , Diyashev I. R.
Published: December 2007

Hydraulic fracturing has been the choice for well stimulation in Russia to enhance production for quite some time now. It was not until recently the treatment design has increased in size and magnitude in order to heed the country’s aggressive production enhancement strategy to meet the local and international demand. The focus of this paper is to discuss the technical and operational applicability of Massive Hydraulic Fracturing (MHF) strategy to enhance production in the Russian oil fields. A case history of the first well that was treated with MHF is provided. The well reflects the large majority of Russian oil wells, especially in the Western Siberian region, which have tremendous potential to enhance production via this strategy. The well falls in the low to intermediate permeability category (less than 1 to 50 md), which can often be converted to be excellent high producing wells by effective hydraulic fracturing technology coupled with proper artificial lifting system. A comprehensive technical analysis of the well before and after the treatment is provided. This includes production analysis using decline and/or type curve analysis before and after treatment, formation evaluation, well performance analysis to estimate the incremental gain, and forecasting. The design and operational aspects of the hydraulic fracturing treatment is also discussed. The results were encouraging. The production increased by more than double after the hydraulic fracturing treatment with relatively low water cut to date. The well was able to flow naturally after the treatment for a few months before artificial lift is installed.
New Dynamic Kill Procedure for Off-Bottom Blowout Wells Considering Counter-Current Flow of Kill Fluid
Authors: Flores-Avila Fernando S. , Smith John Rogers , Bourgoyne Adam T.
Published: December 2007

The "Dynamic Kill" technique has been used to perform off-bottom kills of both, surface and underground blowouts. Usually these kills are designed under the assumption that no kill fluid falls below the injection depth into the upward flow of the formation fluid. If this conservative assumption indicates that the kill is possible to achieve, the operator can confidently proceed with the field operations. However in some cases, calculations under this assumption will indicate that the kill is not possible, discarding a valuable potential solution to the problem. Recently completed research on counter-current flow of kill fluid falling through formation fluid that is flowing upward is applied here to off-bottom blowout wells. This study presents a procedure for controlling off-bottom blowout wells. It relies on the accumulation of liquid kill fluid injected while the well continues to flow to increase bottom hole pressure and assist in killing the well. The method is based on: The critical velocity that prevents control fluid accumulation which can be predicted by a new adaptation of Turner's model of terminal velocity (based on the liquid droplet theory.) This new model considers the flow regime of the continuous phase when evaluating the drag coefficient and the angle of deviation from the vertical.The amount of liquid that flows countercurrent into and accumulates within the well, which can be predicted based on the concept of Zero Net Liquid Flow (ZNLF) holdup.

These two concepts are integrated in the dynamic kill procedure, which is based on system performance analysis to better predict the feasibility of an off-bottom dynamic kill. These concepts were validated with full-scale experiments in a 2787-foot deep research well.
Planning the Well Construction Process for the use of Solid Expandable Casing
Authors: DeMong Karl , Rivenbark Mark
Published: December 2007

In the past, solid expandable casing technology has often been successfully used as a contingency measure to minimize the loss of hole size while dealing with drilling problems. Other applications, such as overall reduction of casing string sizes and numbers, sidetrack applications, and production conformance applications have been slower to attract interest, even though they are all technically viable and economic.

This paper will investigate the process for successfully integrating solid expandable tubulars into all aspects of the well construction program. Preparing the hole section for the installation of the solid expandables will be discussed. Drilling, completion, and production operations through expanded tubulars will also be reviewed.

The process of planning solid expandable projects from conception through well design will be investigated, focusing specifically on the ancillary technologies in the drilling, completion, and production phases. When all aspects of the well construction are optimized, the greatest economic value of solid expandables is achieved at the minimum operational risk.
Underbalanced Drilling For Production Enhancement in the Rasau Oil Field, Brunei
Authors: Sarssam Mark , Peterson Russell , Ward Mike , Elliott Dave , McMillan Scott
Published: December 2007

Underbalanced drilling (UBD) technology has been gaining in popularity around the world because of its capability to reduce or eliminate formation damage, to increase production rates, and in some cases, increase the volume of recoverable reserves. The technology is applicable to fields where formation damage is a concern or where problems such as severe fluid loss, differential sticking, steering problems or slow drilling rates are encountered with conventional drilling.

With underbalanced drilling, the formation pressure is greater than the hydrostatic pressure, allowing hydrocarbons to flow into the wellbore during drilling. This prevents potentially damaging drilling fluids and drilled fines from penetrating the producing formation.

In previous experiences in the field using traditional drilling methods, considerable formation damage had been experienced, and although UBD had never been attempted in the area before, Brunei Shell Petroleum and its government partner decided to use this technology in a three-well trial in the Rasau field, located onshore in Kuala Belait, Brunei.

Of the three wells attempted during this UBD trial one well could not be drilled due to catastrophic borehole collapse. The other two wells were successfully drilled to depth using UBD techniques; however, multiple hole volumes of solids were produced during drilling and production testing, indicating borehole stability problems.

Production rates observed after drilling to TD and prior to running completions indicated zero formation impairment, with well productivity exceeding expectation; however, during the completion phase, mechanical problems occurred, and post completion well tests indicated productivity reductions of 60 to 70% compared with the pre-completion tests. This paper discusses the planning, drilling, results, highlights, and lowlights from this UBD trial, along with learnings and recommendations for future application of the technology. The execution of the program led to a sharp learning curve, and the development of recommendations that can be applied to future operations in this field. These primarily relate to well (construction) design, drilling procedures, equipment design, rig-up and rig-down optimization between wells, and completion design.
Remarkable Results from Water Shutoff Treatments Using a New Deep Penetrating Polymer System—Case Histories from South Umm Gudair Field, DZ-Kuwait/Saudi Arabia
Authors: Al-Mutairi Talal Z. , Shahid Mohammad A. , Reinhold Mark R. , Gazi Naz H.
Published: December 2007

The South Umm Gudair (SUG) field is located in the northwest corner of the Divided Zone (DZ) bordering Kuwait and Saudi Arabia. It represents the southern plunge of Umm Gudair field in Kuwait in the north. The field is producing from the Lower Cretaceous Ratawi Oolite reservoir that is capped by shale limestone sequences of the Ratawi Limestone. The field was discovered in 1966.

There has been significant increase in the water cut throughout the field. The production data in the recent past has shown an increase in water production in a number of wells (50% to 80% water cut) and a resulting drop in oil production.

The field was subjected to three different development phases. In each phase, the Oil Water Contact (OWC) was getting shallower with time. Production logs were run in several wells that indicated water encroachment in individual wells. The reservoir pressure has dropped considerably and all producing wells are completed with electrical submersible pumps.

Efforts made to control the high water cut by conventional mechanical plug back techniques of shutting off the lower perforations were successful in the past but it did not sustain for a longer period of time. The water cone would soon get bigger and encroach the higher perforations with increased water cut, thus the wells would be producing below their optimum potential. It was observed that some advanced technology which could delay the water encroachment more effectively was needed.

This paper describes the case histories of successful applications of a deep penetrating polymer system that was used to create an impermeable gel barrier in the reservoir around the well bore that could sustain long-term water shutoff results in these SUG wells. In addition, the understanding of the reservoir, geology, fluid flow mechanism, and systematic approach of treatment design with proper placement techniques, provided insight into these treatments' success and of limiting the uncertainties involved.

The system was applied to several SUG wells and in all these cases excellent water shutoff results were obtained. Specifically in the first well the water cut was reduced from 71% to less than 1% (0.9%). In another well the water cut was reduced from 72% to 3.4%. In all these cases the oil production was significantly increased.

In addition to the incremental oil gain there is a big reduction in the cost of lifting and handling of unwanted water production resulting in achieving great economic benefits.

The post-job analysis allowed further optimization of these processes, which are facilitating similar applications in the future.
A Novel Laboratory Method for Assessing the Erosional Characteristics of Mudcakes
Authors: Amanullah Md.
Published: December 2007

Design and development of superior drilling and drill-in fluids and also assessment of the effectiveness of mudcake cleaning from the borehole wall by cleaning systems require a good understanding of the fundamental phenomena associated with the erosional behaviour of mudcakes formed by different mud systems. Because of serious consequences of mudcake erosion on formation damage potential of drilling muds and mudcake cleaning prior to a cementation job, it is important to have a suitable, simple and field applicable method for predicting the erosional potential of mudcakes formed by muds of different chemical composition. The prediction of erosion behaviour is essential to screen and select appropriate mud additives and also to design new mud products for producing good quality mudcakes on the borehole wall. The technique and technology could provide a suitable means to assess the effectiveness of mudcake cleaning systems and help design such cleaning systems for removal of mudcake from the borehole wall.

Cakes formed by several water-based muds were evaluated using the newly developed technique. The testing has been performed with the simulation of hydrodynamic conditions corresponding to the drill collar-borehole annular section of a wellbore. The results indicate that the presence of electrolyte significantly increases the erosion coefficient of bentonite mudcake. Ionic fluid loss additives such as PAC (polyanionic cellulose) and CMC (carboxymethyl cellulose) reduced the erosion behaviour of salt water-based bentonite mudcake significantly. However, the presence of polyanionic fluid loss additive PAC caused a drastic reduction in the erosion characteristic of NaCl-based salt water mud compared to the presence of anionic fluid loss additive CMC. The presence of non-ionic fluid loss additive, modified starch shows little improvement of erosional behaviour of salt water-based mudcake. It seems to be that the electro-chemical forces of interactions of ionic fluid loss additives play a vital role in making a mudcake non-erodible. The variation of the erosional characteristic of the mudcakes is attributable to the physical, chemical and electrical properties of the cake forming mud additives and also the nature of the fabrics formed by these additives within the mudcake matrix.
Empirical Heat Transfer Model for Slug Flow and Bubble Flow in Vertical Subsea Pipes
Authors: Gao Changhong
Published: December 2007

The prediction of flow assurance related problems for subsea pipelines, such as paraffin deposition, alphaltene deposition, corrosion, hydrate formation, cold oil line startup etc, all partially rely on valid heat transfer models. Compared with single-phase heat transfer and two-phase hydraulics, two-phase heat transfer is much more complicated because the mechanisms of heat transfer for specific flow patterns are different.

A variety of empirical models have been developed for specific flow pattern of two-phase liquid-gas heat transfer. Some of them have been proved fairly accurate through research and literature review, such as Aggour model for bubble flow and Rezkallah model for slug flow both in vertical pipes. However, when these models are applied to subsea cooling conditions, the accuracy is not satisfactory.

In this paper, the basic knowledge of two-phase flow is introduced. A new empirical heat transfer model is developed for both slug flow and bubble flow in vertical subsea pipelines. Experimental data proves this model works better than the existing models. Literature review indicates that this is the first model that can be applied to two flow patterns. From the results seen, the model can predict good accuracy. The paper therefore recommends the application of this model.
Effective Approach to Horizontal Wellbore Clean-out of Calcium Carbonate Mud Cake in Sandstone Reservoirs
Authors: Uchendu Chike , Nwoke Linus , Arukhe James
Published: December 2007

This paper presents an effective and efficient approach for horizontal well bore cleanout of calcium carbonate mud cake.

The method utilizes a gelled organic acid system, which possesses the unique quality of retaining sufficient viscosity and stability during placement process but still remains active enough to dissolve the calcium carbonate mud cake while in the drain hole 1 . The system offers good leak off control, flow resistance, effective zone coverage and enough capability to flow back the dissolved mud cake to surface.

Ten wells in the Niger Delta were successfully treated with the new cleanout fluid and some of these wells are currently on well potential tests. The placement of the acid was "annulus in, wash pipe out", through the packer port, with the flapper valve on the packer isolating the acid in the drain hole from the brine above it immediately the wash pipe is pulled above the flapper valve. As treatment was incorporated into the initial completions activity, there was no additional CTU mobilization costs.

Field and laboratory results show that complete dissolution of calcium carbonate cake can take six hours and when in solution, can be retained for extensive time with stable viscosity and minimal leak off into the formation.

This paper will report results of laboratory tests carried out to achieve the operator requirements for the treatment fluid; highlight improvements on the initial fluid used and show the unique application and suitability of the gelled organic acid system for certain wells.
A Quick Look Kriging Technique for Reservoir Characterisation
Authors: Brown P. C. , Falade G. K.
Published: December 2007

Correct descriptions of reservoir rock heterogeneity provide useful input for simulation models and are essential for efficient reservoir management.

This paper discusses a novel kriging technique that uses sparse irregularly spaced permeability data to generate permeability values at other points within chosen grid blocks. A uniquely designed computer program, expressed in FORTRAN provides solution to the sequence of algorithms required for the solution of the kriging system in the absence of more sophisticated kriging models. Results obtained from the model allows for relatively cheap and reasonably accurate characterization of heterogeneous reservoirs.
Consolidating the Gains of Rotary Steerable Drilling in the Niger Delta
Authors: Inyang Etido , Edghill Peter , Aniche Victor , Choo Dominick , Adewumi Femi , Olaye Friday , Ogunnoiki Judah
Published: December 2007

A rapid acceptance of the rotary steerable drilling system by the drilling teams of the Niger Delta operators has been occasioned by the increasing difficulties associated with directional drilling in this region. Excluding new discoveries in the deep offshore region, operators have focussed largely on finding economic and competitive ways of exploiting the mature fields already developed beyond the reach of available technologies, and the rotary steerable system presents the opportunity for further development of these fields.

A major operator deployed the rotary steerable system for the first time in Nigeria early 2000. The result was a noticeable improvement in well delivery time, and significant drilling cost reduction for the project. Today, few years after inception, the system has gained wide acceptance and its application has resulted in numerous runs on several projects for these operators, with each reporting marked improvement in drilling performance and significant associated cost reduction. This paper details application of the tool in solving complex field directional drilling problems, ranging from penetration rates to drillability beyond the scope of the conventional mud motor in the Niger Delta.

Improvement modules to the tools facilitated by field experiences and the future of the technology are also discussed.
Estimating Drilling-Induced Formation Damage Using Reservoir Simulation to Screen Underbalanced Drilling Candidates
Authors: Biswas Deepankar , Suryanarayana P. V.
Published: December 2007

In this paper, we illustrate an approach to underbalanced drilling (UBD) candidate selection based on damage assessment and characterization using dynamic reservoir simulations. A 2-phase, 2-dimensional transient reservoir simulator (eRes UBD) using a control volume finite element approach is used to reflect the reservoir conditions. Because of its unstructured grid formulation, the simulator is ideally suited for investigating near-wellbore phenomena, such as drilling-induced invasive damage. In addition, the simulator is augmented to capture dynamic formation exposure, thus enabling drill-ahead capability. Overbalanced drilling conditions are mimicked using the drill-ahead capability of the simulator by specifying an arbitrary depth-vs-time profile, and the resulting formation fluid distribution is investigated, with specific attention to near-wellbore saturation. The impact of invasive damage on productivity is then examined by putting the well into production. Additionally, the extent of damage, flowback period and return permeability are characterized through perturbing critical reservoir and fluid variables. Representative sector simulation runs exhibit the longer term benefits of UBD as compared to conventional counterparts. The methodology described in the paper can ultimately guide the screening and selection of UBD candidates, and is an important part of value-based selection of UBD candidates.
New Tools for Fracture Design Optimization
Authors: Oberwinkler Christian , Ruthammer Gerhard , Zangl Georg , Economides Michael J.
Published: December 2007

Designing an effective and optimum fracture treatment is a complex and time-consuming task, especially in the case of new fields where the number of unknown variables is much larger than the number of known variables. Even with growing field maturity, changes in the fracture design often tend to be marginal and do not lead to a drastic improvement in the fracture design manifested by the post fracture production. This is not say that even marginal treatments are economically unattractive. Fracturing even when done badly is still one of the most economically rewarding petroleum operations. What we are addressing is a much more advanced and refined approach to design where economic benefits can be doubled or tripled.

One explanation for the absence of continuous improvement of fracture treatments is lack of the appropriate tools to perform a thorough data-mining task, which would lead to a definitive improvement in post fracture production benefits.

The appropriate tools for this task are presented in this paper. Although these tools are commonly used in other industries, they are still relatively new to most petroleum engineers.

This paper provides an introduction to the technology and procedures to mine large databases for hidden, but valuable underlying relationships.

An included comprehensive case study presents the workflow of the data mining approach to fracture optimization.

A combination of Neural Networks and Genetic Algorithms, both regarded as artificial intelligence tools, are first applied to the data.

The Neural Network is trained on historic data and captures the relationship between a certain data set of input parameters and the corresponding output parameter. This relationship is stored in the architecture of the Neural Network.

In a following step, the Neural Network is used by the Genetic Algorithm optimization tool to calculate the optimum values for the various input parameters: in this case to maximize the output – the production after fracture treatment. Genetic algorithms are inspired by Darwin's law for the survival of the fittest. For the particular case the fittest values for the different parameter are those, which generate a high post fracture production.

The results are than verified with the Unified Fracture Design approach. Neural Networks use historic data to train. It is required that the data show significant variation to capture the relationships between input and output. Data sets, which show too low variation in production (mainly on the poor side), cannot be optimized based on the artificial intelligence approach. For this case data mining results are integrated into the Unified Fracture Design approach, which will point to the optimum design.

The combination of data mining with an appropriate fracture optimization design approach is a powerful combination in production engineering and one assured to provide large incremental economic benefits to the industry.
Analysis of Off-Balance Fracture Extension and Fall-Off Pressures
Authors: Daneshy Ali
Published: December 2007

Proposal

Three different techniques are presented for detection of the presence and severity of off-balance fracture growth. These are statistical analysis of total friction pressure during mini-fracs, analysis of mini-frac shut-in data, and statistical analysis of main treatment pressures. Most treatments allow application of all these techniques, which will increase the level of confidence in the analysis. All these techniques rely mainly on changes in treatment pressure, not its absolute value. This makes them very suitable for analysis of majority of industrial hydraulic fractures.

Off-balance growth can result in breakage of the bond between the casing and formation. This condition is defined as pseudo-openhole and usually facilitates a better linkage between the wellbore and the dominant fracture, thus reducing the severity of off-balance growth.