bluuebunny/crossref_metadata_2025 huggingface dataset:
Field-Scale Modeling of Asphaltene Transport in Porous Media
Authors: Al-Adhab H. , Kocabas I. , Islam M. R.
Published: December 2007

Asphaltene precipitation can have profound effects on oil production during miscible flooding, heavy oil recovery, or even primary depletion. Even though asphaltene precipitation has been known to have strong effects on permeability reduction, quantitative analysis of the process has been started only recently. This paper extends the previous work to consolidate some of the hypotheses and reports results of a comprehensive field-scale wellbore simulator. The wellbore model couples the asphaltene adsorption model with a series of phenomenological models that are independently validated with either experimental or field data. These models are incorporated into the mathematical model, for a linear as well as radial system. The radial model is particularly useful for simulating asphaltene transport and deposition near the wellbore because of the continuously changing speed for this case. Initially, the simplified governing equations were solved analytically in order to observe the role of some of the parameters independently. Following this, a series of numerical runs was conducted to observe the role of various governing factors on wellbore design parameters under more realistic representation. Experimentally, the deposition was found to be a function of permeability, flow rate and concentration. Two distinct mechanisms were identified, namely, deposition and adsorption. Deposition could be explained in terms of trapping and mechanical plugging. The model builds on the two mechanisms described above. The coupled mathematical model predicts permeability damage due to mechanical trapping and adsorption accurately, as evidenced when compared with experimental results. Three different plugging regimes were identified and were verified with the numerical model. A series of predictive runs further clarified the transition between different flow regimes.
Clean Technology Using Cogeneration Concept for Simultaneous Production of Electricity, Steam and Industrial Gases
Authors: deMontigny D. , Kritpiphat W. , Gelowitz D. , Tontiwachwuthikul P.
Published: December 2007

Energy is the most critical factor for the growth of nations' economy. However, its use has a major impact on the environment especially air pollutants in the atmosphere. In addition, the energy production from fossil fuel, the world most important fuel, is recently known to be the key contributor of the CO2 (a major greenhouse gas) resulting in global warming problems. This paper is an extension of our earlier research work(1) to demonstrate how cogeneration concepts can be used to reduce production costs and simultaneously produce electricity, steam, as well as industrial gases such as CO2. With this cogeneration concept, there will be very little air pollutants discharged into the atmosphere. We will discuss a case study of enhanced oil recovery (EOR) application, conducted at the Energy Research Unit, Faculty of Engineering, University of Regina, Canada. The study was supported by Natural Sciences and Engineering Research Council of Canada (NSERC), Saskatchewan Power Corporation, Saskatchewan Department of Energy and Mines, Prairie Coal Ltd., the Canada Centre for Mineral and Energy Technology (CANMET), Fluor Daniel Inc. (USA), Sulzer Chemtech (Switzerland) and Wascana Energy Inc.
Manpower Recruitment Policy in the UAE: A Survey of the Expatriates
Authors: Sevgur S. B. , Islam M. R.
Published: December 2007

In an ideal work environment, employees are recruited based on their ability and potential of excellence. In order to ensure that bias and prejudice do not prevail, governments around the world have implemented strict recruitment guidelines, especially for workers in the government offices and state universities. Ironically, United States, a country that has been criticized for harboring prejudice for centuries, has pioneered the so-called "Equal Employment Opportunity" regulations and other related laws. While this legislation has yielded some results in some US government sectors, problems have surfaced in other sectors, including areas dealing with technology development and universities. A recent survey of 20 US universities indicates that little attention has been paid to academic excellence in hiring university faculty members. Instead, desperate efforts have been made to recruit members of the "right complexion" and "proper" upbringing. It is interesting to find out if similar practice exists in the UAE. This paper presents a survey of 54 university/college faculty members and employees and 47 employees of the energy sector (all expatriates) in an effort to find trends in hiring practices in the UAE.

The survey indicates that overwhelming evidences of nepotism, ethnic connection, and regional bonding exist. There is no evidence of systematic recruitment of workers who have demonstrated ability to excel. Even announcements and advertisements are targeted to specific ethnic groups.

Unfortunately, this practice is more prevalent in the university/college system than in the industry. Also, there remains a distinct bias in favour of white westerners who enjoy an environment that succumbs to the idea of "white supremacy" (in the minds of many recruiters).

Finally, a series of recommendations is made in order to improve the work environment that currently harbours regionality, ethnic grouping, and other non-technical structures. The UAE government has always shown eagerness in achieving excellence at workplace. This study shows how improvements can be made if proper recruitment policies are exercised.
Displacement Visualization of Gravity Drainage by Micromodel
Authors: Sajadian V. A. , Tehrani D. H.
Published: December 2007

Investigation of physics of fluid flow in porous media at the microscopic scale is expected to result in significant improvement in our understanding of the macroscopic phenomena observed in laboratory and in the field. To model multiphase flow, and to predict ultimate oil recoveries from reservoir formations more realistically, it is essential to study flow behaviour and fluid distribution at the pore level at various situations.

The following results were obtained during secondary and tertiary gas gravity drainage processes: The injected gas changes the balance between gravity and capillary forces and can result in mobilization of connate water and redistribution of all phases.The front will never advance with a horizontally descending gas-oil contact within the pore structure. It appears that initially the buoyancy effects are overshadowed by capillary forces.The film flow of oil is an important phenomenon in the fluid flow process under gas injection.With positive, or near zero spreading coefficient, which is generally the case for most oil reservoir, oil spreads over water and forms a film between gas and water phases. This oil film provides an efficient conduit for flow of oil between various pores under the combined effect of gravity and capillary forces.The displacement efficiency and ultimate recovery decrease significantly for the case of layered network.Oil drainage occurred both, ahead of the gas phase and behind it in the gas invaded zone. As the gas front moves deeper in the model the pressure difference between the gas and oil phases in the gas invaded part increases.
A Note on Impes and Some Impes-Based Simulation Models
Authors: Coats K.H.
Published: December 2007

This paper was prepared for presentation at the 1999 SPE Reservoir Simulation Symposium held in Houston, Texas, 14-17 February 1999.
Kick with Lost Circulation Simulator, a Tool for Design of Complex Well Control Situations
Authors: Petersen Johnny , Rommetveit Rolv , Tarr Brian A.
Published: December 2007

Being able to simulate drilling problems when operating within narrow margins between formation pressure gradients and fracture pressure gradients can cause great savings through improved planning. This is especially the case for HPHT and Deep Water wells. Lost circulation (i.e. underground flow) has in many cases proved to be a significant contributor to complex well control problems and drilling delays.

The advanced kick simulator, RF-Kick, has recently been expanded to include the simulation of massive lost circulation. This tool allows the user to interactively investigate the problems of killing an influx while losses to formation occur. Kill procedures can thus be optimized through simulations.

The fracturing is computed in a simple way. Only three numbers define the fracturing: the Fracture Initiation Pressure, the Fracture Propagation Pressure and the Fracture Closing Pressure. These pressures are supplied by the person using the simulator. The flow into (and out of) the fracture is determined by the flow needed to keep the fracture pressure at the fracture position. A user given fraction of fluid lost to the formation determines the amount of fluid re-entering the well.

This paper presents a description of the model, and a simulation of a representative's deep water well. The simulation starts with a well taking a kick. The well is shut in. As the pressure builds up the formation breaks down and an underground blowout develops. The influx is stopped while limiting the loss to the formation using sufficient flow rate and kill mud. The example describes actions done to lower the pressure at the fracture to stop the loss of fluid, and the careful well operations needed to handle a well with a closing fracture. The simulation finishes when the fracture is closed and all the reservoir fluid has exited the well. Such simulations show the operator what equipment is needed for a successful kill, pump capacity (volume and power), and kill mud (density and volume).

Simulating kick with lost circulation scenarios is novel and a significant contribution. This will enable the industry to perform planning and engineering of complicated well control situations.

P. 25
Integration of Fuzzy Methods into Geostatistics for Petrophysical Property Distribution Simulation of a Reservoir at Exploration Stage
Authors: Zhanggui Lian , Di Jiao , Jun Fan , Jianchun Guo , Kaihong Zhang
Published: December 2007

Theories of fluid flow in heterogeneous porous media show that their transport properties are determined by the structure of spatial correlation in the permeability distribution. Geo-statistical methods have been used to provide equally probable reservoir descriptions that honor available data of a given reservoir for the past decades. During the early exploration stage, the hard data (coring, well testing and well log) often come only from several wells with large well spacing. Though soft data (such as geophysical and geological interpretation, outcrop and seismic data) can be taken into consideration, it is still problematic to characterize a formation by deterministic Kriging or probabilistic simulation, because the formation property spatial variability in different directions is hard to capture by sparse hard data and soft data, especially in lateral direction.

In this paper, fuzzy methods are used to quantify the anisotropy and spatial correlation structure of formation petrophysical properties in a reservoir with several wells and some soft data, and fuzzy methods can be integrated into Kriging, simulation and fractal interpolation. As a result ,some new approaches are suggested and applied to the prediction of the formation property distribution in Shanlan reservoir, West China. Compared to the same methods without fuzziness involved, the techniques show some more robustness and reliability in characterizing spatial variability and structure of the properties and in reservoir characterization.
High Angle Drilling In Severely Depleted Reservoirs
Authors: Bonnett Nigel , Williamson Bob , Oakes Peter
Published: December 2007

The Beryl Field was discovered in 1972, with the Alpha platform coming on stream during 1976 and the Bravo platform eight years later. Platform drilling operations (redrills, following slot recovery) are still ongoing, with the new wells and their associated targets becoming increasingly complex directionally (Designer Wells), in striving to recover the remaining attic oil. These wells generally tend to be horizontal through the reservoir; unless a number of discrete fault terraces are to be penetrated, when a highly deviated wellpath becomes more advantageous, on a productivity basis. However, the major added complication, is the continual depletion of pore pressure of the targeted reservoir sequences. It is now a common feature of these platform wells, to be drilling through the reservoir section with positive pressure differentials in excess of 2000 psi. This paper examines the mature drilling operations on the Beryl Platforms, discusses the philosophy developed to successfully drill under these severe conditions and reviews the operations over the two-year period commencing June 1995.

P. 543
Wireline Tractor Production Logging Experience in Australian Horizontal Wells
Authors: Local Eddie
Published: December 2007

New wireline tractor technology has been developed and used successfully in Australia to deploy production logging tools in horizontal wells. The results of operations in the Wandoo field in Australia are presented. The dynamics of tractor operations have been modelled, and field data has been used to validate the model and to quantify borehole friction coefficients. The model may be used to assist job planning and to assess the feasibility of deployment by wireline tractors in general situations.
Innovative Live Well Perforating System Used in the Statfjord Field
Authors: Kleppa Erling , Svane Elisabeth , Varhaug Helge
Published: December 2007

This paper describes a system developed for live well perforating and presents several case histories of its usage. The system has currently been used on 13 jobs on the Statfjord field. A total of 2106 m has been perforated, and the longest interval in one run has been 277 m in this particular field. The system has been used both for initial perforation on new wells and reperforation in live wells or in combination with zone isolation. Both injectors and producers have been perforated using this system.

An optimum perforating strategy can have significant impact on the economy of a well. During the past few years, techniques to perforate wells without having to use kill fluid have been developed. This reduced the cost and the problems that can occur as a result of kill the well. Kill fluid can not only affect the productivity of the wells, but may also create problems when produced back to the hydrocarbon process equipment. In addition, it has been noted that a higher and more stable sand free production rate will be obtained if the entire interval is perforated simultaneously.1

Perforating underbalanced allows the debris in the perforating tunnel to be cleaned more easily.2 If the well does not have to be killed, considerably less formation damage will occur, and the costs of kill fluid, lifting the well, and handling of the returned kill fluid are also eliminated.

This paper describes a new live well perforating method deployed with a hydraulic workover unit, that allows long intervals to be perforated in wells with complicated well trajectories
A Static Slickline-Retrievable Wellhead Plug System for Use with Horizontal Trees in Offshore Systems
Authors: Vick James , Robb Ewan , Thomson David , Collie Graeme
Published: December 2007

One of the recent enhancements to offshore completion technology has been the development of horizontal subsea trees1 in which the gate valve barrier of a traditional tree has been replaced with a plug system that can be deployed and retrieved with slickline. Traditional plug systems employed elastomeric-type sealing systems. However, because fields with more extreme environments are now being developed, industry trends are showing more metal-to-metal (MTM) seals being requested.

A new static wellhead plug system, which has been developed for horizontal tree configurations, offers MTM sealing capability under all operational conditions. Also, it can be used as a primary barrier that permits vertical access to the well for slickline or coiled tubing well intervention once retrieved through a riser string. This paper will provide background, application, features, testing, and advantages of the new slickline-retrievable static wellhead plugs as well as provide case history data.
Utilisation of a Pseudosonic Curve to Replace Wireline Sonic: a Case History
Authors: Quagliaroli R. , Carugo C.
Published: December 2007

A pseudosonic curve derived from standard drilling parameters has been computed in near real to replace wireline Sonic in a well drilled in offshore Norway.

The pseudosonic curve was obtained using SLDT (Surface Logging Delta Time), a new methodology jointly developed by AGIP and Baker Hughes INTEQ. It is based upon a theoretical Drilling Model that describes the cutting action of various drilling bits using a rock mechanics approach. It employs surface drilling measurements and bit geometry as input data to derive information about formation velocities.

The results obtained for the norwegian well using this novel technology are very encouraging. The ITT (Integrated Transit Time) computed from SLDT data showed an excellent agreement with the ITT derived from VSP run at TD (maximum 0.5% of difference along the well and 0.15% at TD, corresponding at only 2 msec). Moreover, the SLDT curve compared with the sonic wire-line recorded in the 8" 1/2 phase, shows a very good correlation both in absolute values and trend.

The pseudosonic curve furnished a reliable correlation while drilling to offset wireline measurements and to seismic sections.

P. 273
Computer Aided History Matching of a Real Field Case
Authors: Grussaute Th. , Gouel P.
Published: December 2007

This paper presents the application of a semi-automatic history matching tool to real field cases. The process of history matching a reservoir model is a difficult and time-consuming step in the course of a reservoir engineering study. The gradient method has now been widely accepted as an efficient way of aiding the reservoir engineer during this process. The sensitivities of the dynamic observations with respect to the model parameters give some very valuable qualitative and quantitative information about the best history matching parameters.

A history matching tool has been developed to make the most of the gradient information. Tests are carried out on two 3D 3-phase field cases in real industrial conditions. We show that the computing times are still a critical issue for the validity of the method. Results and methodology are presented and the practical benefits of such techniques for the reservoir engineer are assessed.

P. 121
A Novel Technique for Single-Selective Sand Control Completions Cuts Completion Costs in Half: Method Development and A Case History from the Gulf of Mexico
Authors: van Wulfften Palthe P. , Smith J. , Achee T. , Dancause C. , Parlar M.
Published: December 2007

Single-selective sand control completions can be very expensive particularly in offshore environment where rig costs are high. Such completions traditionally involve completion of each zone separately, with multiple trips in and out of the hole. A conventional single-selective completion typically involves a round-trip for each of the following:perforating the lower zone,packing (gravel-frac-) the lower zone,running and setting the packer plug to isolate the lower zone,perforating the upper zone,packing (gravel-/frac-) the upper zone, and finally running in with production string.

The whole process takes anywhere from 8 to 10 days.

In this paper, we present a new technique for single selective sand control completions in cased holes utilizing a single-trip perforating and packing technique with a zonal isolation device for the lower zone followed by perforating with wire line and running in with gravel-pack assembly on production string to complete the upper zone. In this fashion, the completion of the lower zone is reduced from 3 trips 1 trip, and that of the lower zone is reduced from 2.5 to 1.5 trips; with the net savings of 3 trips. This technique required some modifications in the production seal assembly so that the production string could be used as the work string during gravel- or frac-packing. This new completion method was a result of close collaboration between the operating and service company, and has recently been used for frac-pack completion of two zones in a well in the Gulf of Mexico. Completion costs were reduced by 30% and completion time was reduced by 50% compared to alternative traditional methods. Details of tool modifications and the field application are discussed along with economic comparison to earlier practices.

P. 191
History of and Applications for a Coil-Tubing-Conveyed, Inflatable, Selective Injection Straddle Packer
Authors: Loughlin Michael J. , Plante Mark
Published: December 2007

This paper outlines the history, deployment into a live well, and operation of a through-tubing selective injection tool. This tool is an inflatable, re-settable, coiled tubing-conveyed straddle packer assembly designed to run through production tubing and isolate a portion of perforated casing to allow precise injection of stimulation or water block chemicals.

The paper includes a description of 27 field runs of this tool from 1995 through June 1998 and examines the five case histories listed below in more detail:

Gravel pack screen acid wash job Through-tubing selective water shut-off polymer job through casing perforations Through-tubing job to remedially set an external Casing packer (ECP) after completion Open-hole selective stimulation job Through-tubing selective stimulation job through casing perforations.

P. 229
Assessing the Feasibility of a 4D Seismic Reservoir Monitoring Project
Authors: Blonk B. , Calvert R. W. , Koster J. K. , van der Zee G.
Published: December 2007

In many, but not all cases, time-lapse (4D) seismic data can be used with commercial advantage to monitor reservoir changes between and away from the wells. In order to avoid disappointment we need to recognise the favourable cases before starting a time-lapse seismic monitoring project. We aim to assess if a particular seismic survey may be suitable as a base survey and we discuss a 4D-feasibility method, which can be used to predict if predicted changes in the reservoir's acoustic properties could be interpreted using a repeat seismic survey. To this end, seismic, rock and fluid property data, as well as results from the flow simulator are integrated. The method can be used to reduce the risk of shooting a repeat survey that would not show what was being sought, and can also help in deciding on the proper timing for an eventual reshoot. Furthermore, the method is also valuable for assessing data quality before quantitative interpretation studies. The method is illustrated by examples from the Middle East and the North Sea.
Effect of Reservoir Fluid Production on Gas Hydrate Phase Boundaries
Authors: Ostergaard K.K. , Danesh A. , Tohidi B. , Todd A.C. , Burgass R.W.
Published: December 2007

An integrated theoretical and experimental study has been conducted to examine the effect of reservoir fluid production on the hydrate free zone of produced fluids. The paper presents the results of pressure depletion and surface separation of black oil, volatile oil, and gas condensate on the hydrate free zone. The results show that pressure depletion at reservoir temperature has only an insignificant effect on the hydrate free zone of produced fluids, whereas for surface separation, the hydrate free zone of the separated fluids may differ from that of the feed.

P. 507
Combining Innovative Technologies To Maximize Scale Squeeze Cost Reduction
Authors: Bourne Hugh M , Booth Steven L , Brunger Alan
Published: December 2007

The continual need to reduce oil production costs has led Mobil North Sea Limited (MNSL) and TR Oil Services Limited (TROS) to develop a new strategy for maximising the efficiency of scale squeeze treatments on the Beryl Field. The strategy combines the advantages of enhanced precipitation scale inhibitors with a squeeze performance enhancer. The development and use of innovative chemical technologies such as these, has provided the industry with an important new route to achieving cost reduction goals.

The enhanced precipitation scale inhibitor in use on Beryl has been reformulated to provide optimum performance over an eight-hour shut-in period. Core flood studies have shown that the lifetime achieved through use of the optimised product is, in fact, longer than that seen with the original scale inhibitor, which utilised an eighteen-hour shut-in period. The ten-hour reduction of the soak time has meant that production down time during squeeze treatments has been dramatically reduced.

The scale squeeze enhancer has been developed in conjunction with BP Chemicals and BP Exploration to promote the retention of scale inhibitor during a squeeze treatment. Experimental work has indicated that application of the squeeze enhancer in conjunction with the reformulated inhibitor package will result in significantly longer squeeze lifetimes than those previously seen on Beryl.

Following the laboratory work, several field trials in the Beryl Field have been performed. The correct deployment of the enhancer with the precipitation squeeze inhibitor has resulted in a significant reduction in the re-treatment interval and well clean up times leading to significant cost savings.
Electrical Measurements in the 100Hz-10GHz for Efficient Rock Wettability Evaluation
Authors: Bona N. , Rossi E. , Capaccioli S.
Published: December 2007

This paper summarises the experimental and theoretical study conducted in ENI/Agip to investigate the effect of rock wettability on the dielectric response of water and oil saturated core samples. The aim of the study was to evaluate a dielectric technique not previously applied to wettability determination as a practical alternative to conventional tests, and to ascertain the consequent economic and technical benefits in reservoir appraisal.
Use of Tracers in Drilling Muds to Allow the Estimation of In-situ Formation Water Compositions From Drilling-Mud-Contaminated Formation Water Samples
Authors: McCartney Ross A. , de L.G. Solbé Michael J.
Published: December 2007

It has been proposed (e.g. Ref. 1) that formation water compositions can be calculated from drilling mud contaminated sample analyses using a simple mixing model if a tracer is added to the drilling mud. In this paper we test this proposition using field data obtained from 18 wells on the edge of the Irish Sea Basin. Our evaluation shows that, in some circumstances, it is not valid to apply the simple model to Na, Ca, Mg, K, Sr, Cl, Br and SO4 data. Similarly, we have found that apparent mixing trends in data can be misleading and it is important to attempt to validate the results of contamination correction calculations by alternative methods to support formation evaluation and production operations.
Mechanism of a Novel Shear-Sensitive Plugging Fluid To Cure Lost Circulation
Authors: Quinn David , Sunde Egil , Baret J. F.
Published: December 2007

Massive lost circulation is a major and costly drilling problem. The drilling community needs a single fluid which can be pumped through the drill bit, curing losses instantly. This paper describes a novel shear-sensitive plugging fluid designed to gel rapidly after passing through the bottom hole assembly (BHA) in normal drilling operations, thus curing massive mud losses.

This fluid is based upon what is termed a ‘loose’ invert emulsion. The continuous phase provides an encapsulation medium for a crosslinker. The internal phase of the fluid consists of a high concentration of a polymer and the interfacial tension between the two phases is maintained by a concentration of a lipophilic surfactant.

The pressure drop experienced by the fluid as it passes through the BHA triggers the inversion of the emulsion to a direct emulsion. This inversion releases the encapsulated crosslinker into the water phase. The result is a rigid gel which can be designed to generate a solid structure from one to ten minutes after passing through the BHA. The set time is virtually independent of temperature.

This paper describes the perceived mechanism, placement and data from field trials demonstrate the potential of the fluid under difficult conditions.
High-Pressure/High-Temperature Rheology of Na+-Montmorillonite Clay Suspensions
Authors: Rossi S. , Luckham P. F. , Zhu S. , Briscoe B. J.
Published: December 2007

This paper describes the rheological behavior of Na+-montmorillonite suspensions in the presence and absence of different electrolytes (NaCl, KCl, LiCl) and a polyethylene oxide type polymer under high pressure and high temperature conditions. Shear stress - shear rate flow curves were obtained for 5% (w/w) Na+-montmorillonite suspensions for temperatures up to 120°C and pressures up to 1000 Bar. The data was fitted to both the Bingham model and Herschel-Bulkley model, from which the corresponding rheological properties were derived. Results indicate that the addition of electrolytes and a rise in temperature leads to an increase of the yield stress, due to flocculation of the clay suspension and thermal induced swelling respectively. However, the gel structure may be broken down upon the application of pressure depending upon the electrolyte. It was found that the addition of KCl to the Na+-montmorillonite suspensions originated a strongly flocculated structure, less sensitive to pressure variations, where swelling was reduced at higher temperatures. An aggregating behaviour at high temperatures was observed for the clay suspensions containing PEO and either NaCl or LiCl, attributed to the theta-temperature of PEO. At a lower temperature, the presence of PEO on the clay particles allowed the clay suspension to recover after the pressure was applied, preventing irreversible aggregation of the suspension. The rheological properties for PEO stabilised Na+-montmorillonite suspensions containing KCl were very slightly affected under HPHT conditions, in contrast to the presence of other electrolytes (NaCl, LiCl). Swelling of the clay particles was strongly inhibited by the combined use of KCl and PEO. Estimation of the rheological properties of Na+-montmorillonite suspensions in the presence of PEO with the different electrolytes led to the conclusion that the extent of swelling occurs in the order KCl < NaCl < LiCl, coinciding with the order of increasing size of the hydrated cation.
Low Scaling Potential Horizontal Wells and Scale Inhibitor Treatment Strategy
Authors: Raju K. U. , Lynn J. D. , Al-Nasser W. N. , Ayub M. , Hsu J.
Published: December 2007

Oil wells producing from carbonate formations generally experience chemical scaling (carbonates and/or sulfates) during some phase of their production history. In several Saudi Aramco vertical wells, production of formation water containing associated carbon dioxide gas has resulted in calcium carbonate scaling. Scaling potential studies have indicated the threshold level of an organic phosphonate scale inhibitor used to mitigate such scaling in these wells is less than one ppm. This low protection threshold allows considerable leeway in scale squeeze design for the problem wells. Phosphonate based scale inhibitor squeeze treatments provide the most common and effective means of preventing the scale formation in such fields. In vertical well applications, long squeeze lives of more than ten years have been observed in fields producing from carbonates. The residual inhibitor levels have fallen below 0.1 ppm in several of these wells without return of scale.

The increased drilling of horizontal holes and inevitable increases in watercut in these wells have led to scale problems. The design of a viable and economic horizontal well scale squeeze treatment was called for. Considerable problems are, however, inherent in the development of such horizontal treatment strategies. Sorbie, et al., recently published a mathematical scale inhibitor squeeze model for use in horizontal well treatments. This model was used to evaluate several treatment options for horizontal wells having a low carbonate scaling potential. Simulated residual returns and squeeze life data were used for different stages and scenarios in Sorbie's model to arrive at the most optimistic squeeze strategy. Based on the information provided by the model and previous vertical well experience, a simple and inexpensive bullheaded squeeze resulted in a successful treatment. This resulted in a substantial economic savings over a coiled-tubing delivered treatment. The theory behind this simple strategy will be discussed. The results of two case studies will be presented.
A Case Study of Boron Crosslinked Fracturing Fluid in Ultra-Deep Wall
Authors: Yongjun Lu , Yandong Chen , Zhongyang Zhao , Zhenduo Wang
Published: December 2007

The ultra-deep well has a number of characteristics such as high pipeline frictional resistance, high pump pressure in operation, single method for feed flow, high requirements on properties of fracturing fluid and proppant, difficult operation and high cost and investment risk. Fracturing fluid holds the technical key to fracturing operation of a ultra-deep well. As for the characteristics of the ultra-deep, high-temperature, low-permeability and water-injection well in Tarim's DH oilfields, this paper is focused on the properties of fracturing fluid, optimum selection of the additive for organic boron crosslinked hydroxypropyl guar gel (HPG) fracturing fluid and its formulation system including thickener, crosslinker, gel breaker, cleanup additive, fluid loss additive and clay stabilizer, which are suitable for the ultra-deep well in Tarim, presentation on application of fracturing fluid for the high-temperature deep well in Tarim, and analysis and discussion of a number of features of fracturing fluid, such as controlled delayed crosslingking, reduction of frictional resistance, optimization of formula, improvement of rheological property and low damage. The field application indicates that the organic boron crosslinked fracturing fluid is possessed of low frictional resistance, good rheological property, strong sand-carrying capacity, high gel breaking ability and low damage, satisfying the requirements on the fracturing operation for the wells with a depth exceeding 5850 meters.
Stress Corrosion Cracking: AISI 420, 4140, and 1045 on Alloy Steel Used in the Oil, Gas, and Geothermal Industry at Elevated Temperatures in a Hydrogen Sulfide Environment
Authors: Rubiandini R.S. Rudi , Subiatmono P. , Buntoro Aris , Supriyatman Deden
Published: December 2007

Stress Corrosion Cracking (SCC) is the intergranular or transgranular cracking on alloy steel as a result of combination between static stress and special condition. This type of corrosion is usually seen in geothermal, oil, and gas fields, which also produces hydrogen sulfide (H2S) as impurity. At present this problem can not be controlled successfully. To solve this problem, a laboratory study is conducted to determine the rate of corrosion by using three specimens of alloy steel, i.e. AISI 420, AISI 4140, and AISI 1045 which each of it will be simulated in hydrogen sulfide environment with varying pressures and temperatures. Based on the result of the laboratory test, AISI 420 with 13% Cr content is better than the others to solve corrosion problem in geothermal, oil, and gas industry, but the type of stress corrosion cracking for high strength steel (AISI 420) may cause cracking.
Study of Vertical Drilling Technology In High Dip and Application of BHA with Offset Axes Sub
Authors: Su Yinao , Wang Zhenying
Published: December 2007

Straight and fast drilling, especially in high-dip structure, is one of the key technology for deep or superdeep hole drilling, which is a "bottleneck" problem for the deep hole drilling. Based on analysis of its current situation, this paper presents the following technical factors which affect deviation and rate of penetration (ROP): side force on bit, tilted angle of bit and formation deflection force and weight on bit (WOB). The mechanism of hole deviation control, namely the proper treatment of relationship between side force of bit and formation force, is discussed with the affecting factors and calculating method for the treatment. PF plot method, a new method that is utilized to evaluate effects of deviation control and ROP is also brought forward. In this paper, structural characteristics and control mechanism of a state-of-the-art BHA with an offset axes sub (short in OSAS-BHA) designed by the authors are expounded, and its effectiveness shown in Shengke-1, Wei 2-31 wells in Jiangsu Province and Jingshi 1 well in east Sichuan Province is shown in detail. Field application indicated that the OSAS BHA could effectively control hole inclination, and at the same time remarkably increase the ROP in vertical drilling in high dip formations.

P. 145
Delayed Polymer Crosslinking Technique Used for Profile Control in Deep Fractured Reservoir with Low -Permeability
Authors: Wang Zhongmao , Dong Bo , Jiang Yingze
Published: December 2007

The delayed polymer crosslinking technique is used for profile control in deep fractured reservoirs with low permeability. Its mechanism, formulation and injection process have been researched for reservoirs with low permeability, low porosity, heterogeneity and both natural and artificial fractures. The weak gel has a dual function for both profile control and polymer flooding. It is an effective method for improving the flooding efficiency of fractured reservoirs with low permeability and low yield.

P. 169
Condensate Gas Phase Behavior and Development
Authors: Fang Yisheng , Li Baozhu , Hu Yongle , Sun Zhidao , Zhu Yuxin
Published: December 2007

In this paper condensate gas and its main phase behavior, as well as the gas condensate field development characteristics and schemes in China are introduced. Most condensate gas reservoirs discovered in recent years in China are rich condensate gas and some with light oil ring or bottom oil, so their developments are more difficult. Because of commercial demand for gas, usually the blowdown was used in this type of reservoir. In recent years, there are gas cycling field pilots in both Tarim basin and Dagang area in China.

The retrograde condensation and revaporization characteristics during depletion process of condensate gas reservoirs with or without oil ring; displacement oil efficiency using the energy in condensate gas cap and the pilots effects of gas cycling are discussed in this paper. Finally, it is suggested that condensate oil should be produced first and then natural gas using gas cycling under the condition of lacking of both long distance gas pipeline system and downstream installation, which will bring better effects in the development of condensate gas reservoir.

P. 439
Modeling Nonlinear Interactions among Near-Well Flow Restrictions in Well Deliverability Prediction and Simulation
Authors: Hwang M. K.
Published: December 2007

This work describes simulation of well productivity reduction due to near-well flow restrictions. The flow restrictions considered include: mechanical skin, partial completion, altered formation due to residual completion fluid or liquid dropout, and non-Darcy flow effects. It addresses two specific issues. The first is how to predict changes in well performance induced by changes in near-well parameters, as needed in history matching and well test analysis. A subset of this issue is how to estimate the impact of using well parameters to simplify simulation models such as partial completion skin and non-Darcy flow skin, instead of using more layers and solving the non-Darcy flow equation. The second issue is how to accurately preserve well productivity in a large grid block, as in the case of well productivity reduced by liquid dropout in a gas condensate reservoir model. To resolve these issues, this work uses direct simulation and heuristic total skin equations developed for 1D and 2D multi-layered cases with cross flow. The equation correctly represents the effects of nonlinear interactions among near-well flow restrictions on well productivity, resulting in an effective total skin that is much larger than the conventional linear sum of individual skin components. Numerical examples show the total skin equation can be used to predict well performance and to accurately preserve well productivity in a field-scale gas condensate reservoir model. The latter use of the equation shows a feedback mechanism, wherein the total skin is used to adjust the coarse-grid well productivity.
Response Surface Methods for Upscaling Heterogeneous Geologic Models
Authors: Narayanan K. , White C. D. , Lake L. W. , Willis B. J.
Published: December 2007

Experimental design and response surface methods provide a framework for evaluating sensitivities and estimating uncertainties in key reservoir responses.1 In this study, the approach is extended to model upscaled properties such as pseudorelative permeability. Pseudofunctions usually require fine grid simulations for every different reservoir description.2 Response surfaces can be used to generate pseudofunctions for different reservoir descriptions without expensive fine grid simulations. The response surface technique is simpler and cheaper than fine grid simulations and is more reasonable than using the same pseudofunction for different scenarios. This paper applied the response surface approach to waterflooding studies for models based on outcrop exposures of the Frewens Sandstone in central Wyoming.3 The study quantified the effects of different parameters of the reservoir model on the recovery responses and upscaled properties.
Scale-Up of Relative Permeabilities of Isolated Gridblocks Accounting for Boundary Effects
Authors: Suzuki Koichi , Hewett Thomas A.
Published: December 2007

This paper presents a new method for scaling up multi-phase flow properties which properly accounts for boundary conditions on the upscaled cell. Scale-up works by allowing us to omit the simulation of a complete finely-gridded model, but requires us to either make assumptions about the proper boundary conditions for the isolated blocks being scaled up or to determine them in some other way. To date, all scale up methods have made assumptions about fine-scale boundary conditions.

The paper describes how to use the concept of injection tubes (which are hypothetical streamtubes connecting the injection wellbore to all of the inlet-face fine gridblocks of the isolated blocks being scaled up) to determine the appropriate boundary conditions. The use of injection tubes enables us to capture the fine-scale flow behavior of a finely-gridded model at the inlet face of the isolated blocks as if the complete finely-gridded model was simulated. We describe how to scale up a whole finely-gridded model sequentially using injection tubes to determine the boundary conditions for two-phase flow.

This new scale-up method is able to capture almost exactly the fine-scale two-phase flow behavior, such as saturation distributions, inside each isolated coarse-grid domain. Further, the resultant scaled-up relative permeabilities almost perfectly reproduced the average performance of the finely-gridded model. To date, we have confirmed that the method is applicable not only to viscous dominated flow but also to flow affected by gravity for reasonable viscous to gravity ratios.
Scale Up in the Near-Well Region
Authors: Durlofsky L. J. , Milliken W. J. , Bernath A.
Published: December 2007

Scale up techniques are commonly used to coarsen detailed geological models to the scales more appropriate for reservoir simulation. These techniques typically generate upscaled permeabilities through the solution of the local pressure equation subject to some type of linear boundary condition. In the near-well region, coarse scale permeabilities computed in this manner may not adequately capture key features of the fine scale flow. In this paper, we present a general method for computing accurate coarse scale well block transmissibilities and well indexes for vertical wells in two and three dimensions. The method is based on the solution of local well-driven flow problems subject to generic boundary conditions. Simulation results for two dimensional systems indicate that the near-well treatment always provides improved predictions relative to those obtained using standard methods. In some parameter ranges, this improvement is quite substantial. Several three dimensional models are also considered and improvement relative to the standard approach is achieved in all cases. Extension of the method to accommodate complex well configurations could result in significantly improved coarse scale simulations of nonconventional wells.
Predicting the Potential Impact of Synthetic-Based Muds with the Use of Biodegradation Studies
Authors: Candler John E. , Stephen P. Rabke , Leuterman Arthur J.J.
Published: December 2007

The use of synthetic-based muds (SBMs) can improve drilling performance and reduce the volume of pollution generated by offshore drilling operations. Investigations into the environmental impact of SBMs to date have concentrated on the seafloor. The biodegradation rate of an SBM is an important factor in determining the overall environmental performance. Laboratory biodegradation tests are an inexpensive alternative to conducting field studies. However, most of the tests have been designed for water-soluble compounds and reproducible results are difficult to obtain with regularity for hydrophobic materials like SBMs. For this study, a variety of base fluids were tested using the SOAEFD (Scottish Office of Agriculture, Environment and Fisheries Department) solid-phase test. This paper will evaluate SOAEFD solid-phase test results against other biodegradation protocols using a set of criteria designed to identify the best biodegradation test for SBMs.
MABOPP – New Diagnostics and Procedures for Deep Water Well Control
Authors: James John P. , Rezmer-Cooper Iain M. , Sørskår Sverre Kr.
Published: December 2007

The long choke lines extending from the sub-sea blowout preventer (BOP) complicate the procedural difficulties in removing gas as a result of a well control incident. One of the traditional indicators of the ability to circulate out a kick has been the Maximum Allowable Annular Surface Pressure (MAASP). The high choke line friction losses when circulating and gas swap-out in the choke line(s) mean that the use of a constant MAASP (usually based on the last leak-off test) is inappropriate. The use of a dynamic MAASP that can be modeled using a simulator has been suggested as one possible indicator that can allow for the complex interactions between the high frictional losses, gas swap-out, kick tolerance, riser margin and reduced fracture gradients. However, the large fluctuations in this parameter during the kill make its interpretation difficult.

With the advent of instrumented BOP' s, many of the inherent complexities of the kill circulation can be avoided by the use of a new diagnostic: the Maximum Allowable BOP Pressure (MABOPP). Although this is still a dynamic quantity (as it changes during the kill), it avoids the large fluctuations of MAASP as it is isolated from the hydraulic and hydrostatic changes in the vertical choke line(s), and can thus be interpreted more easily. We illustrate the advantages of using MABOPP for deep water well control.

The interpretation of MAASP and MABOPP both involve estimation of the difference between two curves; this is not easy if they are both are changing. We introduce a second diagnostic to alleviate this problem: the ‘Fracture Margin’. This parameter dynamically tracks the difference in the curves and is a direct indicator of the safety pressure available at the last casing shoe.

The temperature effects in deepwater are highlighted and we propose the concept of Hydrostatic Imbalance to quantify the difference in hydrostatic pressure between the drill pipe and annular mud columns.

We also propose a technique of slowing the pumps, while maintaining a constant pump pressure, that is a safe and effective way to minimize the borehole pressure should the choke become fully open during a kill.