bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrating Pressure Transient Analysis in Hydraulic Fracturing
Authors: Rahim Zillur , Buhidma Ismail
Published: December 2007

As part of HWYH Gas Plant development, hydraulic fracturing campaign commenced in 1998 to stimulate the sandstone and carbonate formations in the Ghawar gas fields in Saudi Arabia. To date, over 200 wells have been matrix acidized, acid fractured, and proppant fractured. Whereas post-treatment performance provides a good indication of treatment success, pressure transient analysis (PTA) remains the best approach to determine the effective fracture parameters such as fracture half-length and fracture conductivity. Knowledge of these two parameters is a key element to the optimization of hydraulic fracturing process.
Behavior of Proppants Under Cyclic Stress
Authors: Stephens W. T. , Schubarth S. K. , Dickson K. R. , Snyder E. M. , Doles K. J. , Herndon D. C.
Published: December 2007

Size distribution of proppants is one factor that determines fracture conductivity. Sufficient closure stress can cause mechanical failure of proppants changing the size distribution and altering the bulk properties of the pack. Crush resistance is one characteristic that describes how the size distribution changes under a static load. In many cases, proppants within a fracture experience a dynamic stress state that permits proppant motion and redistribution, altering the stress concentration across the proppant pack.

This paper documents the behavior of proppant size distribution under the influence of cyclic stress. While standard sieve analysis provides a good quantitative value for crush resistance, optical measurement of the size distribution illustrates proppant failure and the alteration of size distribution under load. Advanced load frames permit monitoring and measurement of the compaction process. This paper discusses the sensitivity of the size distribution with respect to closure stress and different types of stress cycles as well as the influence of alternative size distributions and proppant materials.

The results of this paper address expanding the technical evaluation of proppants using new tools and test methods to provide a greater understanding of the evolution of the proppant size distribution. Operators will be able to select proppants based upon data measured under more practical application conditions.
Well-Control Aspects of Underbalanced Drilling Operations
Authors: Ramalho John , Davidson Ian A.
Published: December 2007

Underbalanced drilling is not a new technology. All wells drilled up until the introduction of the rotary drilling rig were drilled underbalanced. However, knowledge of subsurface conditions was limited, well control risks were not managed and well control incidents, when wells struck over-pressured zones, were common. The introduction of the rotary rig, resulted in mud circulation systems. As wells were drilled deeper into over-pressured formations blowout preventers (BOPs) that enabled better well control were introduced. Overbalance (conventional) drilling replaced "underbalance" cable tool drilling and became the normal practice.

In conventional drilling, the hydrostatic pressure created by the mud column provides primary well control and BOPs provide secondary well control.

Underbalance drilling has emerged in the past 15 years, and, just as there have been improvements and refinements in conventional well control equipment and procedures overtime, the same holds true for underbalanced drilling technology. In underbalanced drilling, the primary well control function of the mud column is replaced by a combination of flow and pressure control, while secondary well control functionality is provided by the BOPs. The complete UBD closed-loop flow control system comprises of the drill pipe (DP) circulating system, a UBD control device (UBD-CD), which provides the sealing mechanism around the drill string at surface, a UBD choke manifold (not the rig’s well control choke manifold), a UBD separator and flare system. In addition, non-return valves (NRVs) are installed in the bottom hole assembly (BHA) and drill string to prevent flow up the DP.

This paper provides an overview of underbalanced operations primary well control. It briefly describes the equipment and techniques used and the critical issues to consider during project planning to ensure the safety of staff, the rig, the well and to ensure that the life cycle objectives of UBD wells are addressed.
Characterization of Reservoir Parameters Using Horizontal Well Interference Test
Authors: Awotunde A. A.
Published: December 2007

An analytical solution to transient fluid flow caused by an active horizontal well in an anisotropic reservoir is presented. The purpose of this work is to provide a means to evaluate reservoir and well parameters from observation well pressure response influencing pressure transient created by horizontal wells in reservoirs. This paper further presents dimensionless pressure and pressure derivative suitable for use in characterizing reservoir and well parameters. This work thus presents a model capable of obtaining reservoir parameters at the same time giving a good estimate of effective active horizontal well length from observation well pressure response.

The three-dimensional flow equation is employed and a method similar to that used by the Kelvin heat source solution is used in arriving at the analytical solution. The method of images is used to generate responses across boundaries. Solutions are presented in dimensionless forms for generality and suitability for use in practical field application. Results are then compared with those from existing models.
Measuring Molecular and Thermal Diffusion Coefficients in Multicomponent Mixtures by the Beam Deflection Technique
Authors: Haugen K. B. , Firoozabadi A.
Published: December 2007

We have extended the working equations to determine molecular and thermal diffusion coefficients by the beam deflection technique to multicomponent mixtures. In the past, simultaneous determination of molecular and thermal diffusion coefficients have only been achieved for binaries. Our proposed approach requires transient measurements from (N - 1) laser beams of different wavelengths. The beam deflection technique shows promise of being faster and more accurate than the current techniques to determine molecular diffusion coefficients.
Numerical and Laboratory Assessment of the Oil-Recovery Mechanisms in High-Pressure Air Injection (HPAI) Process
Authors: Niz-Velásquez E.
Published: December 2007

High Pressure Air Injection (HPAI) as an EOR process has found application in high-pressure, light-oil reservoirs, and is particularly promising for low water injectivity reservoirs. Successful HPAI projects have been reported over the last twenty years. However, there is an ongoing discussion on the manner in which the process operates. Several works have pointed out that HPAI can be assimilated to a flue gas drive, since the thermal and associated effects of the oil oxidation would have negligible effect on the overall performance. Meanwhile, calorimetric and combustion tube tests have been used to characterize the operation of HPAI at reservoir conditions. These results are then applied in field-scale simulation models to predict the recovery scenario. Although it is clear that a combination of both gas drive and oxidation reaction effects drives the oil out of the reservoir, the contribution of each process is yet to be quantified.

This work presents a methodology involving experimental tests and reservoir simulation to build a proper simulation model for HPAI at laboratory conditions and quantify the effect of flue gas drive and oxidation reactions on the total oil recovery.

Calorimetric, PVT, flue gas floods and combustion tube tests are available for two light oils. This data is used to extract information about the recovery of each driving mechanism via reservoir simulation. Two- and three-phase (light oil/flue gas/water) displacements are conducted in a foot-long Berea Sandstone core to analyze the effect of saturation history, pressure, temperature and phase composition on the oil recovery at typical process conditions. Same oil species as in the rest of the experimental data are employed. A thermal simulation model for combustion tube tests is built based on the information from individual experiments, and refined by history matching.

Reservoir simulation of a combustion tube test by incorporating history-matched relative permeability curves shows that a flue gas drive process alone cannot explain the high recovery seen in the laboratory.
New Multifunctional Polymeric Additives for Water-Based Muds
Authors: de Almeida Rodrigues J. , Lachter E. R. , de Sá C. H. , de Mello M. , Nascimento R. S. V.
Published: December 2007

The present work had the purpose of developing a new class of polymeric additives for water based muds (WBM), that would present simultaneously several properties needed for a good performance, also being ecologically correct and of low cost. The additives were obtained through the chemical modification of hydrophilic polymers by coupling different hydrophobic segments to one or both end groups. The rheologic analysis of some aqueous systems of the obtained products showed a pseudoplastic behavior, and it is suggested a model to explain the obtained results. A series of drilling fluids was formulated with the best systems studied. The developed fluids successfully played the functions of rheologic modifiers, shale inhibitors, filtrate reducers and lubricants, getting excellent results in Low Pressure and Low Temperature (LPLT) conditions.
Remediation of Production Loss Due to Proppant Flowback through Coiled-Tubing Intervention
Authors: Ingram Stephen R. , Nguyen Philip D. , Hood Al
Published: December 2007

This presentation discusses the results of experimental and field case studies of a remedial treatment technique designed to eliminate fracture proppant production. This process uses a low-viscosity consolidating agent, which is placed into the propped fractures via coiled tubing or conventional tubing coupled with a pressure-pulsing tool. The treatment fluids are designed to provide consolidation for previously placed proppant near the wellbore without damaging the permeability of the proppant pack. The consolidation treatment transforms the loosely packed proppant in the fractures and the formation sand close to the wellbore into a cohesive, consolidated, yet highly permeable pack.

Laboratory gas flow testing indicates that the proppant pack in a fracture model under closure stress required low-strength bonds between proppant grains to withstand high production flow rates. Field case histories are also presented to discuss treatment procedures, precautions, and recommendations for implementing the treatment process. One major advantage of this new remedial treatment technique is the ability to place the treatment fluid into the propped fractures, regardless of the number of perforation intervals and their lengths, without mechanical isolation between the intervals. The fluid placement efficiency of this process makes remediation economically feasible, especially in wells with marginally economic reserves.
World's First Combined Acid Stimulation of Horizontal Openhole Gravel-Pack Application of Coiled Tubing, Dynamically Positioned Vessel, and Floating Production, Storage, and Offloading, Offshore Brazil
Authors: Bogaert Philip , Cavazzoli G. , Perez D. R , Guimaraes C. , Trummer S. , Lungwitz Bernhard
Published: December 2007

Bijupirá is the first offshore field in Brazil to produce oil for an international operator. Since reaching its plateau production in January 2004, Bijupirá has experienced significant production declines. The bulk of the production in the field mainly comes from four sub-sea wells completed with a horizontal open hole gravel pack (HZOHGP). Analysis of the causes of production impairment suggests likely fines migration and possibly BaSO4 scaling.

Scale removal and matrix stimulation treatments were selected as a solution to reestablish productivity. These were performed from a dynamic positioned drillship using CT in the horizontal open hole gravelpacks. The flowbacks were done to the drillship with lift gas supplied from the FPSO. This imposed a very challenging and unique environment for successful implementation.

An extensive laboratory testing program was conducted to determine any negative effects of acid on elastometers and metals used in the wells, subsea system and topsides. Reservoir cores combined with a novel geochemical simulation tool helped to select the acid system and volumes for optimum stimulation treatment whilst limiting possible damage to downhole equipment.

A continuous acid mixing system was designed specifically for this operation to allow handling large volumes of fluids without the need for a stimulation vessel. Fluids were injected via coiled tubing using a special rotating jetting system to ensure mechanical clean-up and diversion. A flow back process was planned, considering the implications of injecting gas from a FPSO to a well, via gas lift valves-recovering hydrocarbons and spent acid to the drillship. This process proved to be effective in eliminating any environmental impact.

This paper describes the whole process including laboratory testing, design, and simulations. Details of the execution phase are given where three scale dissolver and three mud acid treatments were performed with exceptionally outstanding results in terms of execution and production uplift.

The combination of offshore, deepwater, FPSO, drillship and coiled tubing, set a milestone in the industry as first worldwide intervention of this kind.
Fiber-Optic-Enabled Coiled-Tubing Operations on Alaska's North Slope
Authors: Escarra P. D. , Sorman I. , Blount C. G. , Woods N.
Published: December 2007

Fill cleanouts, matrix stimulation, cementing, and downhole milling are some common coiled tubing (CT) operations. The difference between the success and failure of these jobs relies heavily on the knowledge and prediction of the behavior of downhole parameters such as temperature and pressure. Another significant percentage of CT operations depends on highly accurate depth control to ensure the intended result of the operation. These depth-critical operations include setting packers, tubing patches, CT-conveyed perforating, and zonal isolation. And in virtually all CT operations, including fill cleanouts, stimulations, and cementing, the knowledge of an actual tied-in depth is advantageous to operations.

The purpose of this paper is to present a simple and reliable system that allows real-time monitoring of downhole pressure and temperature, and provides depth correlation using a casing collar locator (CCL). In this system, the downhole parameters are recorded in real time without the limitations of conventional wireline-enabled coiled tubing units.

The information presented in this paper summarizes the operations performed during the field-testing of the system at Alaska's North Slope. Twenty-seven CT operations were successfully performed using the system; this demonstrated its reliability and provided the crew with the information needed to improve the efficiency of the operations being performed.

The system comprises three main components: Downhole tools capable of measuring and transmitting bottomhole pressure and temperature as well as identifying casing collars with high accuracy.Fiber optic and fiber optic carrier, which provides real-time transmission of downhole data to surface.Wireless bulkhead and surface interface modules to provide two-way communication between the tools and the monitoring system.
New Tubingless Sucker Rod Pump System in Slimholes
Authors: Yonghui Liu , Yingchuan Li , Zhenzhi Li , Xiyan Fan , Xingfu Zhou
Published: December 2007

In this paper, slim hole refers that the nominal diameter of production casing is less than 5 inch. In many problem wells, production casing is destroyed and new casing is reinstalled to continue oil production. And sidetrack drilling in old well is an effective method to find residual oil. Slim-hole drilling is widely used in low productivity, low permeability or low reservoir pressure oilfield for low drilling cost. So the number of slim-hole wells increases quickly. None of artificial lifts turns out to be a good option in slim well. The sucker rod pump system is mainly used. As a result, pump depth and daily fluid production rate are limited by the slim tubing, and oil test isn't available because of the small annulus.

The new tubingless sucker rod pump system can solve some of these problems. It adopts a packer to suspend tail pipe and seal the annulus between tail pipe and the casing, and fixing mechanism and sealing mechanism work together to fix pump system and seal the joint between tail pipe and pump system. Consequently the flow passage of the fluid is built: the mixture from the reservoir flow in tail pipe, then enter pump system to increase the pressure and eventually come into the annulus between rod string and the casing through special screen section. The pump efficiency is high and the production cost is greatly reduced for the tubing string is omitted and most of the conventional equipments are used.

The new system was successfully used in 4 inch and 51/2 inch casing wells in Zhongyuan oilfield, increasing the daily fluid production rate, as compared to the conventional sucker rod pump system. This paper presents description of the new tubingless sucker rod system, and reports the results obtained in two stages of field tests. The design method is also given.
Methods of Using Logs To Quantify Drillability
Authors: Andrews R. , Hareland G. , Nygaard R. , Engler T. , Munro H. , Virginillo B.
Published: December 2007

Correlations between sonic logs and the formation drillability for different lithology types have been developed from data taken from 10 wells in North America. The gamma ray log was used in conjunction with drilling data to calculate the drillability. The drillability from penetration rate models is back calculated from bit design and reported field wear in conjunction with meter by meter operating parameters, formation type and pore pressure. Then this drillability was correlated with sonic logs for different lithologies as defined by the gamma ray log. The different formation types clearly show different correlations for the normalized correlations between drillability and sonic logs. The non-homogeneous lithologies are also correlated and normalized to rock strength from the sonic logs where the percent formation type mixtures are determined from the gamma ray.

Data from multiple wells is presented showing the accuracy of the presented approach where more then 100,000 data points were statistically analyzed and evaluated in the development of the equations presented herein.

The drillability from inverted penetration rate models has been verified to give good representation of rock strength based on comparison with triaxial laboratory data and makes the use of this model more versatile. The correlations provide improved estimations of rock strength which can be used in drilling performance simulation and wellbore stability studies.
Reorientation Refracturing Case Study
Authors: Yao Fei , Weng Dingwei , Li Yang , Yu Yongbo , Hou Feng
Published: December 2007

This paper consideres how the initial hydraulic fractures and the oil and gas wells production/injection impact on initial stress field, and forms the stress field prediction software. Applied the software in Xinzhan Oilfield, 5 layers of 4 wells which might be reorient were selected from 19 layers of 7 wells. In the treatment of these wells, tiltmeter was used to monitor how the fractures propagation. After refracturing, the production histories of the wells were matched. The results show that the reorientation occurred in the refracturing of experiment wells, and so the validation of the software was verified.

Introduction

Reorientation refracturing is that some measures are taken in refracturing process to make the refracturing reorientation. At present, more and more fields and wells need to be refractured. Refracturing has two ways: 1.fractures spreading along original fracture azimuth, 2. fractures spreading along a new azimuth different from original azimuth, reorientation refracturing belongs to the latter. As we know, fractures always spread along the azimuth vertical to the minimum principal stress, so the stress field after the first hydraulic fracturing determines the fractures breakdown and spreading. The research on change trend of stress field could direct the refracturing, predict fractures azimuth and decide the best refracturing opportunity.1–2

The theory of the stress field prediction

No matter what refracturing reorientation induced by principal stress reorientation or that induced by shear stress change making fractures spread along shear plane, the original stress field change is the basic dominating factor.

The existence of the first hydraulic fractures and the production of wells, the anisotropy of reservoir, the fractures and injection or production of neighboring wells cause the change of original stress field, and may make the stress reorientation. In these factors, the existence of the first hydraulic fracture and the production of wells are the most important ones.3 The physical models (Fig. 1) are used to describe stress induced by the existence of the first hydraulic fracturing:4 a plate with a 2 a long linear fracture, the fracture has the same thickness with the plate, and the tension on the fracture is - P. The principal stress and shear stress in x, y, z direction induced by the first hydraulic fractures can be described by the following formulas:
Detection of Impacts in a Changing and Highly Variable World: The Case of a Floating Storage and Offloading (FSO) Unit in the Gulf of Paria (Venezuela)
Authors: Cruz-Motta J. J. , Petkoff Irene , Klein Eduardo , Alvarez Haymara
Published: December 2007

Studies of environmental impact assessment (EIA) base their final conclusions and/or decisions, typically, on available information that has been extracted from existing environmental studies. To solve this, conclusions and desicisons taken after an EIA can be re-stated in the form of hypothyeses, and the appropriate monitoring programs are put in place to test them. These monitoring programs should be designed to detect the potential impacts that a given development might cause. An important aspect to be developed to reliably detect an anthropogenic impact is the development of an effective and precise analytical framework able to differentiate between human induced changes and the natural spatio-temporal variability shown by most populations. Among all the possibilities, "Beyond-BACI designs" allow addressing unequivocally these issues, but until the beginning of the millennium their use was limited to the analysis of single variables (e.g. abundance of a single species or any measure of biodiversity). In this paper we describe an asymmetrical sampling design that will allow the use of an analytical procedure able to unambiguously detect if there is any effect of a FSO on the natural conditions of the surrounding marine areas and assemblages living in it, more specifically, pelagic and soft-bottom benthic assemblages. The FSO will be located in the Gulf of Paria, Venezuela.

The proposed sampling design consists of one potentially impacted location (1 km radius area around the exact location of the FSO) and three reference locations (same area as the impacted one) sampled at two spatial scales: three sites within each location (separated by 2 −3 km) and replicate units within each site (separated by 100´s of meters). This spatial layout of sampling sites will be sampled three times before and three after the placement of the FSO.

In this study, the comparison of the different variance components for the assessment of potential impacts will be done using a recently developed multivariate method: dissimilarity-based permutational MANOVA, for the analysis of multi-species data matrices in response to complex sampling designs such as the one described above.

This type of experimental design and associated analyses are complicated and require a considerable increment of replication effort beyond to what we are accustomed to, involving costs above what has traditionally been the case. This expenditure, however, is warranted because, among other reasons that will be discussed in the paper, it does protect against unfounded claims of impacts, and realistically determines the level of a predicted impact so that corrective or mitigating options can be developed and implemented.
16Cr Coiled-Tubing Field Trial at Prudhoe Bay, Alaska
Authors: Julian J. Y. , McLellan B. J. , McNerlin B. J. , Martin J. R. , Van Arnam W. D. , Normoyle B. K. , Tipton S. M. , Burke K. W.
Published: December 2007

Sixteen chrome coiled tubing (16Cr CT) was introduced in the spring of 2003 and over 200 strings have been put into field use as velocity strings. Following preliminary testing, two 16Cr CT reels were deployed at Prudhoe Bay, Alaska to evaluate feasibility as an intervention workstring. The two reels performed a variety of standard CT applications on a daily basis. Observations and data were gathered to determine operating guidelines, applicability, and limitations. The field trial indicated that 16Cr CT can be deployed in the field with only minor operational modifications.

16Cr has superior abrasion resistance in 13Cr production tubulars and little CT surface (external) wear was seen during the field trial. The second reel developed a pinhole failure earlier than expected; however, analysis of the adjacent material indicates that 16Cr has increased low cycle fatigue life when compared to standard carbon steel CT. Additional testing is ongoing, and it is felt that the conditions resulting in the failure can be mitigated to avoid future premature failure.

This paper documents the lab and field trial results. Standard operating procedures for 16Cr CT are described that provide easily implemented guidelines. 16Cr has applicability as an intervention workstring, particularly in corrosive environments and in areas where abrasive 13Cr production tubulars must be endured.
Coiled Tubing Cement Packer Repair at Prudhoe Bay, History and Current Techniques
Authors: Julian J. Y. , Sack J. K. , Johns J. E.
Published: December 2007

Packer repair utilizing CT is an important non-rig remediation in the greater Prudhoe Bay Area, Alaska where rig workover costs are significant. To date, approximately 22 CT packer repairs have been performed with a 100% success rate. This high success rate has resulted in investigating possible improvements in efficiency. These are primarily associated with reducing cement and plug milling operations.

This paper presents the history of packer leak detection and repair at Prudhoe Bay. Diagnostics are detailed, including conventional logging methods with temperature, spinner, and waterflow logs. Additionally, the newly developed ultrasonic leak detection log is described. This tool has the ability to detect ultra small leaks and has led to an increase in number of candidates.

Cement packer repair design is discussed, as well as detailed CT operation guidelines. Recent improvements and optimizations to techniques are presented along with areas for future investigations.
The Successful Application of Underbalanced Drilling Technology for Reservoir Evaluation and Drilling Performance Improvement in Kuwait
Authors: Vieira P. , Larroque F. , Al-Saleh A. M. , Ismael H. , Qutob H. H. , Chopty J. R.
Published: December 2007

The Shuaiba formation in the Raudhatain field is a highly fractured limestone reservoir. Conventional drilling technology in this formation usually results in a complete loss of drilling fluids to the formation. These losses cause severe formation damage which results in masking the evaluation of the potential for hydrocarbon production.

Underbalanced Drilling Technology was proposed as an alternative drilling method. The main objective of the UBD drilling application was to evaluate the potential of hydrocarbon in the Shuaiba formation while simultaneously eliminating fluid loss to the formation and improving drilling performance.

This well was the first well drilled underbalanced by KOC, a training program was prepared in order to familiarize the rig personal involved with the operation of the UBD equipment and procedures. The openhole section was drilled out of a 10 ¾" casing with an 8 ½" bit. A conventional mud pulse MWD/PWD/LWD tool with real-time annular pressure, temperature and gamma ray sensors were incorporated in the BHA. The use of MWD/PWD/LWD provided a means of monitoring the downhole underbalanced conditions and formation properties while drilling. The Shuaiba formation was successfully drilled underbalanced without any fluid loss during the drilling phase. The openhole section was drilled to a total depth (TD) of 8942 ft MD, with an openhole length of 242 ft.

Integrated efforts of KOC and service companies of various disciplines during planning and operation stages of the well led to the success of the project. No QHSE incidents were reported.

This paper highlights the key factors in the underbalanced drilling design phase, the operational challenges faced, and the results of the first well drilled in Kuwait using underbalanced drilling technology.
Pipeline Flow Capability Restoration Using Coiled-Tubing and Rotating-Jetting Technology
Authors: Acosta Marco , Santamaría Juan , Moss Paul , Rivera Herman , Mosquera Julio , Robles Mario , Barragán Fernando
Published: December 2007

Problems associated with Pipeline flow capacity reduction due to the presence of Scales, Asphaltenes and Parrafins have always been present and are well documented. Solutions to these problems are not however as well understood or discussed and, more often than not, complete replacement of the affected section is imminent because of the limited solutions available to the operator. Completely changing a section of Pipeline can have significant costs associated with it. Indeed, material & labor costs, environmental impact due to Pipeline construction and loss of flowing capacity represent the key reasons to avoid this type of operation if at all possible and give reason for ongoing investigations into possible alternatives.

This paper outlines a solution that was implemented several times in Ecuador whereby Coiled Tubing employing rotating & jetting technology was used to completely restore Pipeline flow capability without the need to replace any section of the affected tubular.

This solution involved the use of proprietary rotating/jetting technology introduced into the Pipeline at strategic locations, defined by computer simulations, to affect a successful cleanout operation. Selecting an efficient cleaning fluid was also very important for the success of these operations as there were significant economical and environmental limitations that had to be overcome.

Details about this solution, including defining the operational limitations of the Coiled Tubing material due to restrictions, orientation and curvature as well as fluid selection and other design limitations and considerations are included in this paper.
A New Approach for Phase Behavior and Well Productivity Studies in the Deep Gas-Condensate Reservoir With Low Permeability
Authors: Zhilin Q. , Wang Shouping , Du Zhimin , Liang Baosheng , Deng Ruijian , Zhao Wei
Published: December 2007

Deep gas-condensate reservoirs, with high temperature, high pressure, and low permeability, account for a high proportion in the recent years. Quite different with conventional gas-condensate reservoir, this type of reservoir has smaller rock grains, prominent interfacial phenomena, and appreciable reservoir deformation. Consequently, it is necessary to study phase behavior and well productivity to model these deep gas-condensate reservoirs more accurately.

This paper considered both interfacial effect and reservoir deformation, and proposed a new method for calculating oil-gas phase equilibrium in deep gas-condensate reservoirs. We introduced phase equilibrium calculation into fluid flow theory for condensate oil and gas system and then mathematically developed a physical-chemical flow model with consideration of interfacial effect and reservoir deformation. Gas well productivity was also studied and the corresponding equation was derived. Because flow behavior near wellbore is essentially important for a gas-condensate reservoir, we investigated fluid flow near wellbore and provided methods to determine retrograde condensate saturation, gas relative permeability, and pressure distribution.

We applied to a real gas condensate reservoir and calculated well productivity, retrograde condensate saturation distribution, and gas relative permeability, particularly near wellbore. The results illustrated that interfacial phenomena and reservoir deformation made retrograde condensation appear much earlier and consequently aggravate formation damage. Therefore, the decrease of gas relative permeability and the drop of well production are faster than usual.
A New Darcy-Stokes Flow Model for Cavity-Fractured Reservoir
Authors: Peng Xiaolong , Qi Zhilin , Liang Baosheng , Liu Xueli
Published: December 2007

Conventional cavity-fractured reservoir has small sizes of cavity and the corresponding flow behavior is presented by the equivalent model for fluid flow in porous media. However, in Tarim Basin, the biggest land oil/gas-baring basin in China, many unconventional fractured reservoirs are found that cavities are the main storage space while both fractures and cavities offer flow paths. Current porous flow model are not applicable due to the large cavities even with the scale of meter. A new flow model is needed to describe the flow behavior in order to successfully develop these cavity-fractured reservoirs.

In this paper, fluid flow in Tarim cavity-fractured reservoirs is firstly studied by integrating geology and reservoir engineering. As an example, Tahe Ordovician carbonate reservoir is analyzed in detail. Then, a new Darcy-Stokes model for slightly compressible two-phase flow is built. In our model, flow area is divided into porous flow region and free flow region according to flow characteristics. Porous flow region obeys Darcy's law and is described by the flow in porous media with multiple porosities. On the other hand, free flow region satisfies Navier-Stokes flow and the equation describing slightly compressible two-phase flow is developed. The connection at the interfaces of these two flow regions is derived by the extension of Beavers-Joseph-Saffman boundary condition to two-phase flow.

The application of Darcy-Stokes flow model to Tahe reservoir demonstrates that this model gets better prediction on oil production performance than the fractured model with dual porosity.
Performance Evaluation of Acid Treatments in Injector Wells With Reference to Division Techniques
Authors: Beheiri Faisal I. , Nasr-El-Din Hisham A.
Published: December 2007

Numerous acid stimulation techniques have been employed in water injectors to achieve uniform distribution across the injection interval. Mechanical and chemical diversion techniques were utilized separately and jointly to eliminate high permeability zones or thief zones where most of the injection water is flowing into a thin layer of the injection profile. The choice of placement techniques and chemical diversions plays an important role in the treatment success.

This paper presents case histories of acid treatments performance evaluation based on placement and diversion techniques. Based on the calculated time-lapsed injectivity index model and flow-meter surveys, the effectiveness of various mechanical and diversion techniques were evaluated. Placement techniques were either using bullheading or coiled tubing technique. The study covered 49 treatments using bullheading technique and 33 treatments using coiled tubing technique. The chemical diversions included polymer and surfactant-based in-situ gelled acids and foam diversion.

Flow meter survey conducted on several seawater injectors indicated that polymer-based acids damaged some zones of the injection interval. This resulted in poor distribution of the injected water. Foam diversion using bullheading technique did not improve the injection profile in the presence of thief zones. Wells treated by placing the acid using CT showed better performance than those wells treated by placing the acid by bullheading. Combinations of mechanical (CT) and chemical diversion (foam) showed better results than using chemical or chemical diversion alone. Viscoelastic surfactant-based acid showed significant increase in the injectivity index.
Proactive 3D Geosteering Boosts Productivity and Recovery in Complex Clastic Environment
Authors: Al-Dossari Salih M. , Al-Shobaili Yousef , AlHadhrami Mohsin , Nasr Raed , Babayeju Oludiran
Published: December 2007

Traditionally, the steering of horizontal wells has been based on logging-while-drilling measurements that rely on the sensors to actually measure the formation's characteristics when drilling through it and then use this information to make the correct steering decision. This approach is a reactive one, however. The implementation of deep and directional electromagnetic measurements that can detect approaching boundaries enables us to implement a proactive steering approach.

Another key element of the new approach is the ability to make geosteering decisions to change the well trajectory in both inclination and azimuth. This is a critical success factor when dealing with a channel sand environment, where the shape of the sand bodies is not well delineated by seismic data.

This challenging work calls for multidisciplinary collaboration and integration of techniques to succeed in maximizing the net-to-gross ratio obtained from drilling horizontal laterals in such environment. Similar collaboration has been facilitated using a workflow that helped the geosteering operation run effectively, even within a large geosteering team from different backgrounds and companies.

In this paper, we look at case studies where the new technique has been implemented. We discuss aspects that lead to the success of this approach and the learning points gathered from the case studies are presented as well.
Reducing Incidents in Marine Personnel Transfer
Authors: Strong Philip A.
Published: December 2007

Millions of crew transfers take place each year and whether they are by boat or helicopter, this remains one of the highest risk activities in offshore operations. Although the safety of crane transfers compares favorably with other methods of crew supply, incidents and associated litigations are not infrequent.

Why does such an ‘apparently simple’ operation go wrong? One reason is a lack of recognition of the true risks. Operators go to great lengths to improve the safety of helicopter operations, whilst marine transfers rarely get a second thought. The underlying objective, however, remains the same; to move personnel to and from their place of work in a safe, cost effective and reliable manner.

This paper looks at the real risks, the root causes of recorded incidents and outlines how transfers can be made safer. Risk can be managed in two ways:

Engineered protection – A modern car provides a secure environment that can protect passengers from impacts. A transfer device can do the same and guard against the inevitable human factors that contribute to the majority of incidents. Improved operational control – Procedures, pre-lift planning, communications and training can all play a significant role in reducing risk.

The paper also describes how analysis of past incidents led to the development of improved equipment and operating practices. Considerable focus was given to ‘human factors’ to prevent minor misjudgments, for example by a crane operator or a vessel skipper, leading to serious incidents.

After ten years working with enhanced systems and after millions of safe transfers, the author explains why serious transfer incidents are not an inevitable feature of offshore life. Modest investments and changes in operational practices have provided many operators with a dual benefit of safer operations and reduced downtime.

Finally, the author takes a look at the future of offshore crew supply, providing details of a ground breaking new project that will utilize a state of the art high speed catamaran and newly developed transfer system. This will be the first time that a vessel and transfer system has been custom built to provide swift, comfortable and safe transfers to offshore installations. The system, dubbed ‘Crew-Express’, is due to be commissioned in the Gulf of Mexico in late 2007.
Comparison of Stabilised/Solidified Mixes of Model Drill Cuttings Based on the North Sea and Red Sea Areas
Authors: Al-Ansary M. S. , Al-Tabbaa A.
Published: December 2007

Following the global stringent legislations regulating the wastes generated from the drilling process of oil exploration and production activities, the management of hazardous drill cuttings has become one of the pressing needs confronting the petroleum industry. Most of the prevalent treatment techniques adopted by oil companies are extremely expensive and/or the treated product has to be landfilled without any potential end-use; thereby rendering these solutions unsustainable.

The technique of stabilisation/solidification is being investigated in this research to treat drill cuttings prior to landfilling or for potential re-use in construction products. Two case studies were explored namely North Sea and Red Sea. Given the known difficulties with stabilising/solidifying oils and chlorides, this research made use of model drill cutting mixes based on typical drill cutting from the two case studies, which contained 4.2% and 10.95% average concentrations of hydrocarbons; and 2.03% and 2.13% of chlorides, by weight respectively. A number of different binders, including a range of conventional viz. Portland cement (PC) as well as less-conventional viz. zeolite, or waste binders viz. cement kiln dust (CKD), fly ash and compost were tested to assess their ability to treat the North Sea and Red Sea model drill cuttings. The dry binder content by weight was 10%, 20% and 30%. In addition, raw drill cuttings from one of the North Sea offshore rigs were stabilised/solidified using 30% PC. The characteristics of the final stabilised/solidified product were finally compared to those of thermally treated cuttings.

The effectiveness of the treatment using the different binder systems was compared in the light of the aforementioned two contaminants only. A set of physical tests (unconfined compressive strength (UCS)), chemical tests (NRA leachability) and micro-structural examinations (using scanning electron microscopy (SEM), and X-ray diffraction (XRD)) were used to evaluate the relative performance of the different binder mixes in treating the drill cuttings.

The results showed that the observed UCS covered a wide range of values indicating various feasible end-use scenarios for the treated cuttings within the construction industry. The leachability results showed the reduction of the model drill cuttings to a stable non-reactive hazardous waste, compliant with the UK acceptance criteria for non-hazardous landfills:

(a) by most of the 30% and 20% binders for chloride concentrations, and (b) by the 20% and 30% of compost-PC and CKD-PC binders for the Red Sea cuttings. The 20% and 30% compost-PC and CKD-PC binders successfully reduced the leached oil concentration of the North Sea cuttings to inert levels.
Barium Sulfate: A Protocol for Determining Higher Site-Specific Barium Cleanup Levels
Authors: McGinty Jim , McHugh Thomas E. , Higgins Elaine A.
Published: December 2007

Although different barium compounds are known to exhibit vastly different toxicities, cleanup standards for barium in soil or sediment at environmental corrective action sites are typically based on total barium concentration without regard for the specific barium compounds present. However, the Texas Commission on Environmental Quality (TCEQ) has recently agreed that the insoluble barium compound barium sulfate (i.e., barite) is not a compound of concern with regard to human health, thereby eliminating the need for cleanup standards or site remediation for this compound. The TCEQ still requires that their barium cleanup standards be applied to any soluble barium compounds that may be present at a site. To allow the application of barium cleanup standards to soluble barium compounds while excluding barium sulfate, we have developed a protocol to measure the concentration of soluble barium in soil or sediment samples that may contain both barium sulfate and soluble barium compounds. In this paper, we present (1) a review of the toxicity and regulation of soluble barium compounds and insoluble barium sulfate, and (2) a description of our protocol to measure the concentration of soluble barium compounds in soil and sediment samples and the validation of this protocol.
Mapping and Monitoring the Petroscape in Venezuela's Heavy-Oil Belt With Landsat and CBERS Satellite Images
Authors: Baynard Chris W.
Published: December 2007

A study is made of petroleum infrastructure expansion, or petroscape, in three of Venezuela's four heavy oil operations between 1990 and 2005. A change detection method using Landsat and CBERS satellite imagery and a GIS is implemented for gauging estimates in land use and land cover change (LULCC). The objective is to determine which Associations showed the greatest and least reduction in biomass tied to petroscape growth in a time series corresponding to the before, early and full production phases. Results indicate variability in the amount of land use dedicated to petroleum infrastructure among three (of four) operations which consists of partnerships between the state oil industry and multinational oil companies (MNOCs).
Predicted Impacts From Offshore Produced-Water Discharges on Hypoxia in the Gulf of Mexico
Authors: Bierman Victor J. , Hinz Scott C. , Justic Dubravko , Scavia Don , Veil John A. , Satterlee Kent , Parker Michael E. , Wilson Scott
Published: December 2007

Summer hypoxia (dissolved oxygen < 2 mg/L) in the bottom waters of the northern Gulf of Mexico has received considerable scientific and policy attention because of potential ecological and economic impacts. This hypoxic zone forms off the Louisiana coast each summer and has increased from an average of 8,300 km2 in 1985–1992 to over 16,000 km2 in 1993–2001, reaching a record 22,000 km2 in 2002. The almost 3-fold increase in nitrogen load from the Mississippi River Basin (MRB) to the Gulf since the middle of the last century is the primary external driver for hypoxia.

A goal of the 2001 Federal Action Plan is to reduce the 5-year running average size of the hypoxic zone to below 5,000 km2 by 2015. After the Action Plan was developed, a new question arose as to whether sources other than the MRB may also contribute significant quantities of oxygen-demanding substances. One very visible potential source is the hundreds of offshore oil and gas platforms located within or near the hypoxic zone, many of which discharge varying volumes of produced water.

The objectives of this study were to assess the incremental impacts of produced water discharges on dissolved oxygen in the northern Gulf of Mexico, and to evaluate the significance of these discharges relative to loadings from the MRB. Predictive simulations were conducted with three existing models of Gulf hypoxia using produced water loads from an industry study. Scenarios were designed that addressed loading uncertainties, settleability of suspended constituents, and different assumptions on delivery locations for the produced water loads. Model results correspond to the incremental impacts of produced water loads, relative to the original model results which included only loads from the MRB.

The predicted incremental impacts of produced water loads on dissolved oxygen in the northern Gulf of Mexico from all three models were small. Even considering the predicted ranges between lower- and upper-bound results, these impacts are likely to be within the errors of measurement for bottom water dissolved oxygen and hypoxic area at the spatial scale of the entire hypoxic zone.