bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a novel Silicone Rubber/Cement Plugging Agent for Cost Effective Thru' Tubing Well Abandonment
Authors: Bosma M.G.R. , Cornelissen E.K. , Reijrink P.M.T. , Mulder G.S. , de Wit A.
Published: December 2007

Large scale well abandonment campaigns will soon become a major cost issue for most Operators. Traditional well abandonment comprises the removal of the production tubing followed by well plugging by mechanical plugs (as primary seal), backed up by (potentially non sealing) cement plugs.

The classical abandonment operation is very costly, especially in an offshore environment, since it requires the utilization of a workover or drilling rig. Significant savings could be achieved if wells could be abandoned by a Coiled Tubing operation, during which the production tubing could be left in- situ.

After long negotiations, a major Dutch Oil and Gas Operator (NAM, Nederlandse Aardolie Maatschappij), convinced the legislative body of the Dutch Mining Department (SodM) that non workover rig assisted abandonment operations could be equally reliable as conventional abandonment methods provided certain operational precautions were taken. This entailed the rigorous cleaning of the production tubing and production liner by solvents and hot surfactant flushes and the utilization of (rotating) jet nozzles on CTU prior to setting of the sealing plugs. Furthermore, in critical (gas prone) wells special attention had to be devoted to the plugging material itself, since it now had to fulfill the duty of the mechanical seal, as well. Inherently, it had to display much-improved sealing characteristics (gas tightness, resilience, bonding) compared to conventional cement formulations.

Novel Silicone Rubber/Portland Cement plugging materials have been developed for this application at Shell International Exploration and Production, Research and Technical Services (SIEP-RTS). This paper describes the laboratory development and screening (Sealing Ability, Mechanical Characteristics, Setting Kinetics, and Adhesion) of various candidate sealants and the optimization of these characteristics for a large scale well abandonment campaign.

Trial well abandonment's using the new sealing agent(s) in NAM's Schoonebeek and Ijsselmonde/Ridderkerk Fields are discussed.

P. 483
Reviving the Job Signature Concept for Better Quality Cement Jobs
Authors: Piot Bernard M. , Loizzo Matteo
Published: December 2007

The Job Signature concept was introduced long ago but was never widely implemented throughout the industry. This paper will discuss first the use of combining data acquired during the cement job with a simulator to analyze the well cementing process and derive information as to the quality of the cementation. Case studies illustrate the reliability of the simulator and therefore indicate the level of confidence when the same simulator is used for design purposes.

The concept of "job signature" can safely be extended to the evaluation process, and most of all to those cement jobs for which design or execution data are not complete, or extreme well whose conditions cannot be completely simulated.

The systematic use of this evaluation technique relies not only on people's experience and competence, but also on the user-friendliness, availability, and efficiency of the sofiware. Progress in monitoring cement job data and in simulator user- friendliness with the advent of PC-based machines running in a WindowsTM environment, now allow this technique to develop rapidly as an efficient evaluation tool.

Combined with an animated graphic interface, the generalized use of the simulation tools enables the engineer to produce a Job Signature at the wellsite in a minimum amount of time, without requiring expertise in computers or job evaluation.

Finally, further progress of the software in integrating the different simulators (centralization, U-tube, mud removal, circulating temperature) and working real time on the data acquired during the cement job are outlined.

P. 505
Multi-Lateral Well Construction: A Multi-Benefit Drilling Technology
Authors: Winton J.A.C. , Lodder R.J. , Smit A.L.
Published: December 2007

Application of multi-lateral well engineering has been successfully applied as an emerging technology in the Northern North Sea to drain more marginal reservoirs which would otherwise be uneconomic. Calibration of the technique to local conditions is vital and the success in the North Sea offers tremendous follow-on opportunities for global applications.

Following a successful onshore trial, Shell Expro's Northern Business Unit and their lead well engineering contractor, KCA Drilling Ltd, drilled and completed TA-14, a cased hole multi-lateral. This consisted of an appraisal and subsequent abandonment of the Triassic formation, followed by the drilling of two geosteered horizontal laterals into the shallower Brent reservoir. Techniques developed on TA-14 were then employed on an existing well. TA-19, to suspend the mainbore, side-track and recomplete as a dual lateral. Re-entry exists into the horizontal lateral with continued production available from the mother bore. Recently, TA-17 has been completed as a dual lateral horizontal Triassic oil producer with selective production from, and re-entry capabilities into both cased hole laterals. One lateral developed Triassic reserves proven by TA-14 while the other appraised the neighbouring block.

A steep learning curve has been experienced throughout the construction of multi-lateral junctions. This includes the milling and fishing process, management of debris and equipment design. Further well engineering strategies for cementing, clean up, perforating and completions have been developed.

Benefits of the multi-lateral technique are pervasive. Savings on TA-14 type wells can be achieved by applying the technique in a combination of variable and low quality reservoirs in one single well. Slot constraints can be alleviated using the TA-19 technique by side-tracking existing producers at an earlier stage. This strongly accelerates production whilst safeguarding the often underestimated tail production from the mother borehole. By using the TA-17 technique, two objectives can be met from one borehole, which would have otherwise required two new wells.

Lessons learnt have accelerated the evolution of multilateral systems on the Tern and applications have been identified for multi-laterals in early and mid 1998. Other future applications of the multi-lateral methods are expected to involve coiled tubing drilling and water injection wells with a very large economic window of opportunity.

P. 523
Through Tubing Infill Drilling as a Method for Increased Oil Recovery on the Gullfaks Field
Authors: Vikane E. , Samsonsen B. , Lorentzen K.E.
Published: December 2007

The Gullfaks Field (GF) has been in production for ten years and 2/3 of the estimated reserves have been recovered. Due to the complex structural geology and the extreme permeability contrast there is still large volumes of oil in closed pockets and bypassed areas of the field which are not economical to develop by conventional drilling methods. The primary drilling program on the Gullfaks A and B platforms are completed and new drilling targets tend to have smaller volume and more risk.

This formed the background of the project "Let one Hundred Wells Flow" (LHWF). A small team of drilling-, completion- and petroleum engineers was formed with the objectives to identify and map small oil pockets and propose economical solutions to drain them. Different suppliers of drilling- and completion equipment and -services gave important contributions to the solutions. The project was performed over a six month period and resulted in identification of 34 targets containing 8.5 10 6 Sm3 recoverable oil.

Coiled Tubing Drilling (CTD) is considered to be the preferred way of drilling side-track through tubing. This is a fairly well established field-proven technique, it is cost effective and it is suitable for drilling through small ID production tubing.

The first coiled tubing sidetrack has been drilled. The side- track was a success and CTD is now regarded a qualified method on the Gullfaks Field.

P. 573
A Global Drilling Organization: The Role of the Drilling Professional
Authors: Boykin George F.
Published: December 2007

This paper is the second of two that describe how Amoco's Exploration and Production Technology Group's (EPTG) Drilling organization is meeting the challenge of building a global drilling organization. The first paper described the performance measures, systems and structure we have chosen, and why we believe these are ones that best suit proper application of drilling technology. This paper's purpose is to promote a healthy discussion of the role of a drilling professional, and what drilling organizations should and can do to promote drilling as a profession.

The previous paper discussed the hard side' of the drilling management equation (processes, rewards, strategy, and measurement), this paper addresses the people side of the equation: professionalism, staffing, culture, compensation, and demonstrating the value of people.

P. 581
Experiences on New Types of Drilling Contracts
Authors: Caraballo C. H. , Bastidas G. E. , Torres A. J.
Published: December 2007

Today's energy necessities have produced an increment in drilling activities all around the world. Among this situation is the fact that all the operators are trying to minimize cost without reduction in quality. So, they are looking for new types of contracts between all drilling companies, Contractors, services and suppliers. In this paper, we will present some experiences in types of drilling contracts in east Venezuela. It will include some operational benefits and difficulties that will come up while applying each type of contract. It is important to point out the highest commitment of all companies involved versus traditional day-rate contracts. So far, as a drilling contractor new contracts have involved INTEGRATED DRILLING AND WORKOVER SERVICES, with Operator. ALLIANCES with Operator and Major Services Companies. BONUS-PENALTY based in an operational target time. LUMP-SUM with Operator. CREW INCENTIVES with Operator. Another type of contract that is called DRILLING SERVICES MANAGEMENT is just starting to develop soon. Results show that in all the cases, if drilling crew is considered and a higher participation of the drilling contractor is permitted, it has created a structure to add real value on drilling activities. Additionally, the application of each new type of contract depends on operator necessities and the commitment of each drilling contractor and service company to take the challenge.
Technology Improvements in Platform Slot Recovery and Liner Removal
Authors: Bailey T.F. , Neff M. , Wilson T.L.
Published: December 2007

Liner removal to facilitate sidetracking has been proven to be a cost saving solution over drilling new horizontal wells to increase production from existing wells. Most problems that might be encountered when removing casing can be identified prior to beginning a liner removal job. By identifying these potential problems, the proper equipment can be used effectively to keep the job running smoothly. Technical advances in mill design such as the development of a cutting structure that effectively manages the cuttings size and carbide inserts with greater wear resistance have increased the efficiency of the entire operation.

P. 641
Eliminating Heave Induced Difficulties in Critical Multilateral Casing Exit Operations
Authors: Blizzard Bill , Luke Mike
Published: December 2007

Advanced downhole milling operations are difficult, if not impossible to perform from a floating vessel. Semisubmersibles, drill ships and other "floaters" maintain heave compensation equipment to accommodate typical drilling operations, however, when weight on bit (WOB) must be tightly controlled, these systems fall short of meeting the requirement. A new technique has been developed whereby rate of penetration (ROP) is the controlling element in milling, not WOB. This ROP approach requires specialized equipment and procedures and was first developed to allow sensitive milling operations to be performed during the installation of a multilateral wellbore junction from a semi- submersible drilling vessel in the North Sea. This paper examines a Subsea Downhole Motion. Compensation (SDMCTM) tool that was instrumental in the success of that multilateral junction.

P. 659
Mobile Offshore Jack-Up Units – The Next Generation
Authors: Rimlinger R.
Published: December 2007

Drilling Technology advancement, reduced time frame from hydrocarbon reserve identification to production and movement to deeper water depths and harsh environments necessitates a reusable Mobil Offshore Jack-Up drilling / production design. The paper will discuss the technological design advancements along with potential cost reductions associated with utilizing a single structure; Jack-Up Unit; performing simultaneous drilling, production and workover operations in harsh environments and deeper water depths.
The Development of Automated Drilling Rigs
Authors: Reid David
Published: December 2007

Handling tools have been improved and adapted, wherever possible, to aid remote automation on today's drilling rigs. Work that was done manually using elevators, spinning chains, tongs and brute force is now managed by using remotely controlled machines.

The application of automation to improve the performance of drilling rigs has captured the attention of the drilling industry for years. Numerous rig designs have been tried with relatively few success stories. The history of drilling automation can be paralleled to the development of Pipe Handling Systems on the drilling rig floor.

This paper offers examples to support the theory that there are four critical developments required to achieve automation on the drill floor.

P. 695
Hybrid Coiled Tubing System for Offshore Re-entry Drilling and Workover
Authors: Selby Bruce , Srinivasan Nagan , Donnally Bob , Vincent Randy , Wilke Jerry
Published: December 2007

In coiled tubing offshore re-entry drilling and workover operations, a jack-up pulling unit or an independent mast has traditionally been used to pull pipe out of the wellbore before the coiled tubing services could be employed. This method of operation often becomes cumbersome and costly. An innovative coiled tubing (CT) drilling system that offers an alternative method to the conventional techniques has been introduced to the oilfield. The new system, the hybrid coiled tubing system (HCTS), integrates the coiled tubing injector, the power unit and the reel into a transportable rig with a mast.

The concept and design of the methods and equipment were developed to respond to the need for servicing shallow to moderate-depth oil or gas wells in the Gulf of Mexico. In this area, typical well specifications range to 10,000 ft measured depth; and wells are usually directionally drilled from multiple-well, fixed platform structures or in shallow inland waters.

A specific case history is outlined to show the utility of using hybrid CT instead of a conventional rig for the type of work required. Operational efficiency and safety advantages are evident in mobilization, demobilization, speed of rig-up and rig-down, and in the reduction of time needed for tripping into and out of the well.

This system provides a cost efficient solution to the need for a re-entry system for offshore use.

P. 23
Proactive Safety Approach for Well Construction in Alaska's Kuparuk River Field
Authors: Petrash D.M. , Graff A.O. , Trantham J.A.
Published: December 2007

In 1995, the Kuparuk Drilling Group (KDG) recognized that safety performance had continually improved since well construction commenced in the Kuparuk River Field in 1981. However, it was also recognized that performance improvement appeared to be losing momentum. Upon analysis of the trend, it was noted that most efforts to reduce workplace risk were focused on 1) engineering controls; 2) administrative controls and operating practices; and 3) personal protective equipment.

In order to return to improving safety performance, attain world class status, and help employees return safely from the workplace to their families, the KDG solicited input from the drilling contractor to develop and implement a proactive behavior-based safety program. Part of the development included a goal-driven incentive, the Safety Performance Goals Program, which de-emphasizes safety statistics and fully complements the overall safety objectives.

P. 771
New Facets of Universal Fluid Usage: Reduction of Hole Wash-Out and Solidification for Environmentally Safe Drilling Waste Disposal
Authors: Nahm J.J. , Wyant R.E. , Rask J.H. , Thant Myo , Cannon Gene
Published: December 2007

Two new benefits derived from the use of a Universal Fluid (UF) have been demonstrated:reduction of the hole washout volume andsolidification of excess drilling fluid and drill cuttings for environmentally acceptable on-site waste disposal.

A UF containing about 30 lb/bbl blast furnace slag was used as a drilling fluid while drilling a recent south Louisiana well in an effort to reduce hole washout and to demonstrate that the solidification of the UF and drill cuttings would provide an environmentally safe material which remains on-site and can be used for location maintenance, road construction, and land fill or other uses.

The UF was used while drilling a 9 7/8-in. hole from 3,125 ft to the casing depth of 10,600 ft. The slag content ranged between 25 and 30 lb/bbl, while the UF weight was increased slowly from 9.4 lb/gal to 12.2 lb/gal. Caliper logs indicated that the average diameter of the UF-drilled section was 10.88 in., considerably better than the 12.85 in. of the same section of a previously drilled offset well. Of the total 147,000 lb of slag used, about 30% remained in the UF, about 22% was deposited as filtercake, and about 21% was discharged with the cuttings through solids control equipment.

A concept of rig-site drilling waste management involving solidification of the UF wastes is elaborated and related lab and field data are presented. The necessary amount of slag for solidification is already in the UF and solid wastes, but additional slag can be added depending on the final product firmness desired. To demonstrate the waste solidification process, an additional 20 lb/bbl slag was mixed with a 40-barrel batch of the excess waste in a "V," -bottomed auger tank. The UF mixture was allowed to harden on location and successfully used for land fill. This paper shows that the UF can protect the drilled wellbore and can be economically treated and used for on-site disposal.

P. 785
Early Kick Detection Through Liquid Level Monitoring in the Wellbore
Authors: Schubert J.J. , Wright J.C.
Published: December 2007

Through the years many tools have been developed to detect kicks in their early stages, when they can be handled more easily and safely. However, most of these tools are dependent upon the well being full of fluid with the liquid at the surface. When drilling wells where there are severe lost circulation problems (e.g., no returns to the surface) many of the major kick detection tools do not function properly since the liquid level may be hundreds or thousands of feet below the surface. During tripping operations, the major kick indicator is measurement of the volume of drilling fluid required to "fill" the hole to replace the volume of steel removed. If the annulus cannot be filled, again due severe losses to the open formation, measurement of the fluid pumped into the annulus does not give meaningful information as to formation fluid influx until the influx is great enough to begin to unload the annulus.

This paper proposes the use of an acoustic device installed on the casing valve to continuously monitor the liquid level in the annulus of wells experiencing complete loss of returns. A rise in liquid level can be interpreted as an early indication of a kick during drilling or tripping operations. The liquid level can also be used to determine the correct volume of fluid to pump into the well while tripping out of the hole.

This paper presents the results of tests run using common acoustic tools to monitor the liquid level in the wellbore of an Austin Chalk re-entry. Results of these tests show that the liquid level can be accurately monitored during complete lost returns so that kicks can be detected early during drilling or tripping operations.

P. 889
New Insight into the Mechanisms of Shale Inhibition Using Water Based Silicate Drilling Fluids
Authors: Bailey L. , Craster B. , Sawdon C. , Brady M. , Cliffe S.
Published: December 2007

There has recently been a resurgence in the use of water based muds containing sodium silicate for drilling reactive shale sections, particularly in the North Sea. The performance of these silicate water-based muds (SWBM) has been mixed: they are extremely effective in inhibiting swelling and dispersion of claystone and chalk, however some concerns exist over the stability of the system in terms of fluid properties, long term wellbore stabilisation and lubricity. This paper details new results, previously unreported, which give a better insight into the mechanism of clay stabilisation using SWBM.

Recent literature has suggested that silicate fluids are as effective as oil-based muds (OBM) in wellbore stabilisation.

This paper describes research and development indicating that silicate precipitation occurs within shales to form a barrier or membrane that hinders ion movement. However, there are distinct differences between the efficiency of membranes produced by oil based and silicate water based muds. Results are included which demonstrate that the ion- exclusion membrane is not as effective with Silicate systems as it is in OBM. New core flow experiments demonstrate that a permeability reduction with silicates and a slow rate of ionic equilibration are the principal causes for the osmotic barrier seen in swelling tests.

Further results indicate a change in the physicochemical nature of clays after exposure to high pH silicate fluids. It appears that redistribution of alumino-silicate occurs which may play an important role in the inhibitive nature of these fluids.

These evaluations are placed in context with well data in which primary considerations are the nature of any lost time incidents and overall SWBM performance.

P. 897
Whipstock Performance Review in Gulf Coast Region Yields Operational
Authors: Hinojosa Robert , Ryan Jimmy , Wyman Richard , Wiley Barton
Published: December 2007

When sidetracking a wellbore the decision must be made whether to cut a section or mill a window in the casing. There are specific instances when setting a whipstock and milling a window is the better option. The performance of whipstocks is dependent both on certain well parameters and post milling operations. The parameters such as depth, hole angle, cement status, casing size, weight and grade, and distance to be drilled to a large degree are fixed. Post milling operations seem to present the best avenue to ensure good window performance.
Investigation on Formation Damage Control of the Methylglucoside Fluids
Authors: Zhang Yan , Chen Zhu , Yan Jienian
Published: December 2007

The invasion of mud filtrate with associate fine particles may impair rock permeability around the wellbore. The control of formation damage induced by drilling muds has long been recognized as part of good drilling practice. Utilizing the muds with improved filtration control characteristics provides an efficient method of limiting the extent of damage. It is highly desirable for drilling muds to form an impermeable mud cake quickly, thereby reducing the spurt loss and cake thickness. The Methylglucoside fluid, designated as the MEG fluid, is a recently developed environmentally acceptable water-based mud and its performance approaches the oil-based muds. Previous investigations have shown that the MEG fluid is very shale stabilizing, and has superior lubrication and filtration control properties.

This paper presents the experimental procedures, results and analysis performed on formation damage characteristics of the MEG fluid. Core flow tests were conducted using the MEG fluid and three other commonly used drilling muds. Two types of sandstone cores with high and low permeability were used in the experiments. The depth of invasion of filtrate and fine particles present in the MEG fluid were evaluated. Laboratory results have shown that the MEG fluid is superior in the formation damage control, Compared with conventional drilling muds, the extent of damage caused by filtrate retention of the MEG fluid is smaller and the return permeability is higher. Also, the MEG fluid has an excellent property of filtration control.

To investigate the mechanism of why the MEG fluid controls formation damage, a series of experiments were conducted which include the cake texture observation, the particle size distribution analysis, inhibition evalution and the measurements of surface and interfacial tension etc.

P. 241
Water Base Drilling Fluid Replaces Oil Base Mud to Control Formation Damage
Authors: Ray Ananda Kumar , Singh Lehmbar , Dinesh R. S. , Singh Daljit
Published: December 2007

Alpha field is a sand stone, mixed drive reservoir, located in Cambay Basin of India. The exploitation of the reservoir continued since 1969 resulting in decline in reservoir pressure which in turn made drilling of infill wells, avoiding formation damage difficult. The reservoir was to be put on polymer flooding for which 16 infill wells were to be drilled. A few infill wells drilled in past had shown high formation damage. High mud weight was found to be the root cause. Therefore oil base mud was experimented in one well resulting in no formation damage but at high cost. On economic consideration it was thought to try low gravity water base drilling fluid in one well with a change in the prevailing casing policy. The strategy worked and the well so drilled and completed resulted in no formation damage. The same strategy was followed in remaining infill wells and all of them were successfully drilled. The field trial thus demonstrated how application of low gravity water base drilling fluid with judicious casing policy can control formation damage and may be better alternative to costly non-conventional method like oil base mud.
Physics and Modeling of Permeability Damage Induced by Particle Deposition
Authors: Chauveteau G. , Nabzar L. , Coste J-P.
Published: December 2007

The different mechanisms leading to permeability damages due to particle deposition are analyzed under various situations relevant for oil production. The analysis is based on the relative importance of the forces involved in the various deposition processes. In this way, different deposition regimes, characterized by the values of a few non-dimensional numbers, are defined. Among the major parameters, some are conventional and usually considered, such as particle and pore sizes, flow rate, particle concentration and suspending fluid viscosity. However, other parameters, which are often ignored, such as particle and pore shape and roughness, particle-particle and particle-pore wall interaction energies as well as pore surface physicochemical heterogeneity play an even more important role. In all cases, the regime determines deposition kinetics and the location where particles are deposited inside porous structure. As a consequence, determining both the deposition regime and the mechanism of permeability damage involved are prerequisites before any attempt to model and to predict permeability reduction. Due to the complexity of practical cases, experiments must be carried out to define the regime and the values of the major parameters used as input in a suitable formation damage model. Comparisons between model predictions and experimental results obtained under well-controlled conditions show the cases where presently the permeability damage modeling is reliable.

P. 409
Frac Packing Using Conventional and Alternative Path Technology
Authors: Shepherd Don , Toffanin Ezio
Published: December 2007

This paper discusses a completion technique that has been applied in Saudi Arabia with good success in minimizing skin damage in very high permeability oil wells that require sand control.
New Acidizing Techniques Prove Useful in the Offshore Environment
Authors: Harvey R. , Smith C.J. , Wylie M.P. , Eberhard J.E. , Chapman B.J. , Vitthal S. , Gidley J.L.
Published: December 2007

Acidizing oil wells in sandstone formations often causes a variety of problems, ranging from inadequate productivity response, and unwanted stimulation of water, to the upsetting of surface separation facilities. A simple, economical, and effective change in the procedure for conducting these treatments involves displacing the oil from the zone to be acidized with a miscible gas, preferably CO2. Such displacement, often called preconditioning the formation, prevents interaction between the acid, its reaction products, and the resident oil. Field results with this treatment indicate an improved productivity response, less stimulation of water, and reduced emulsion separation problems at the surface.

Previously published information on this process was taken from a single field offshore Louisiana and involved the use of conventional mud acid (HF/HCl)1. The results in this paper demonstrate that the use of CO2 has wide applicability to offshore fields and works satisfactorily not only with conventional mud acids but with a variety of organic acids as well, is to inject into the formation a preflush, normally hydrochloric acid, to displace connate water and to remove the carbonates. In some cases, organic acids (either formic or acetic) are employed instead of HCl to avoid problems with the mineralogy of the formation. The second step involves injecting an HF-containing acid to react with clays, feldspars, and other materials thought to be the source of damage. The mixture most often employed is one of HCl and HF, although organic acids are sometimes substituted for HCl because of the sensitivity of certain formations to HCl.

P. 515
Aluminum Scaling and Formation Damage due to Regular Mud Acid Treatment
Authors: Nasr-El-Din H.A. , Hopkins J.A. , Shuchart C.E. , Wilkinson T.
Published: December 2007

Accurate formation damage identification significantly improves the success of a remedial stimulation treatment. In an oil-producing well in Central Saudi Arabia, the electrical submersible pump (ESP) used to lift the oil from the well was damaged and needed to be replaced. Production engineers observed a deposit on the impeller of the pump. The deposit was also suspected of plugging the formation and significantly reducing oil production.

Laboratory analyses of the scale deposit by XRD, XRF, and SEM revealed an amorphous material containing a high concentration of aluminum. After extensive examination, it was determined that the only possible source of aluminum was a previous HF stimulation. Examination of the well history showed that a typical 12% HCl-3% HF mud acid stimulation treatment was conducted during the original drilling and testing of the well. 9F NMR spectroscopy indicated that the deposit contained F/Al molar ratio of 0.4, consistent with precipitation from completely spent HF fluids. Solubility showed that 70 to 85 wt% of the deposit could be dissolved with 15 wt% HCl, if it could be contacted.

A retarded HF acid based on aluminum chloride was designed to remove the deposit and improve well productivity. A wellbore clean-out with 10 wt% HCl was conducted to remove very near wellbore deposits. In addition, a large HCl preflush, twice the volume of the HF stage, was pumped before the retarded HF to remove deposits within the formation. All acid fluids contained 2–5 wt% acetic acid and 50 lbs/Mgal of citric acid to prevent precipitation of aluminum and iron.

Special efforts were made to recover spent acid fluids. Return fluid samples were collected throughout the flowback. Complete fluid analyses are discussed along with their implications. Considerable acid spending was observed from dissolution of the aluminum deposits and carbonate minerals. The presence of carbonates suggests precipitation of aluminum within the formation matrix.

The retarded HF treatment design successfully removed aluminum precipitation damage from the previous HF treatment. Production of the well stabilized at nearly twice the pre-stimulation levels with no further re-occurrence of the aluminum scaling problems.

P. 539
Upscaling of Reservoir Properties Using Wavelets
Authors: Jansen F.E. , Kelkar M.G.
Published: December 2007

The wavelet transform has the ability to preserve local structures in spatial data sets. This paper presents a technique by which wavelet transform is used to upscale the fine scale permeability values in 2 and 3 dimensions. The method is easy to implement and very efficient. Although not based on preserving the physics of the flow process, it is able to capture the flow processes in both 2 and 3 dimensions. Further, the method also compares favorably with other upscaling techniques.

P. 23
Capillary Pressure Correlation for Mixed-Wet Reservoirs
Authors: Skjaeveland S.M. , Siqveland L.M. , Kjosavik A. , Hammervold W.L. , Virnovsky G.A.
Published: December 2007

For water-wet reservoirs, several expressions may be used to correlate capillary pressure, or height above the free water level, with the water saturation. These correlations all feature a vertical asymptote at the residual water saturation where the capillary pressure goes to plus infinity.

We have developed a general capillary pressure correlation that covers primary drainage, imbibition, secondary drainage, and hysteresis scanning loops. The graph exhibits an asymptote at the residual saturation of water and of oil where the capillary pressure goes to plus and minus infinity, respectively. The shape of the correlation is simple yet flexible as a sum of two terms, each with two adjustable parameters and is verified by laboratory experiments and well-log data. An associated hysteresis scheme is also verified by experimental data.

The correlation can be used to make representative capillary pressure curves for numerical simulation of reservoirs with varying wettability and to model and interpret flooding processes.

P. 39
Depositional Model of the L-III Horizon in a Sector of Bombay High South Field and Its
Authors: Sharma P.K. , Abdurahman Kutty , Rautela P.S. , Shrivastava R.K.
Published: December 2007

The Lower Miocene L-III limestone reservoir of Bombay High South, Western offshore, India, is a multi-layered reservoir. It has been divided conventionally from top to bottom into major layers A, B, C, D, E, and F separated by intervening shale and argillaceous tight limestone. A' layer is further subdivided into Al, A2-I, A2-lI, A2-III, A2-lV, A2-V, A2-VI and A2-VII and along with layer B constitutes the main producing horizon. Identification and mapping of individual layers and facies distribution in them has important implications in the effective reservoir management as well as performance prediction. The present paper attempts to work out a depositional model for these layers through integration of log, core and reservoir data in order to explain the spatial and temporal variations in the distribution of poro-perm characteristics of flow units.

Based on log characters and core data, a tidal depositional model has been evolved. It has been envisaged that the carbonate layers have been deposited in a tidal regime comprising supratidal, intertidal and subtidal environments. Though the deposition has taken place in shallow lagoonal conditions, the reworking effect of the tidal waves in a regressive regime has given rise to the carbonate deposits in the tidal channels and adjacent levees, and shale in the marshes. These layers have also witnessed subaerial exposure. Starting from C and B layers, during their deposition, the environmental conditions were uniform without much facies and thickness variation and the area had an open marine influence as indicated by the presence of pelecypod shells and other associated fauna. These layers, along with the overlying N shale, have been designated as Sequence I. The overlying A2 -VII and A2-VI layers, deposited in a subtidal regime are termed as Sequence 2. The layers A2-V and A2-IV represent an intertidal regime and constitute the Sequence 3. Finally, the carbonate cycle ends with intertidal environment having influence of supratidal regime comprising the layers A2-IIl, A2-lI, A2-I and Al. The occurrence of microdolomite/ dolomitic wackestone in this sequence supports the presence of supratidal environments. The sequences are identifiable on GR log showing diagnostic log features.

In general the area has been under the influence of a regressive cycle during the deposition of sequences 1 to 4. At micro level, however, each stratigraphic sequence has witnessed deposition of different facies due to fluctuations in bathymetry. In the ultimate analysis, the model will provide significant leads about reservoir facies changes in time and space and help in recognizing the horizontal and vertical poroperm variations in the different flow units of the prolifically producing L-III horizon.

P. 677
Rigless Techniques Enhance the Effectiveness and Economics of Water Shut-Off
Authors: Farooqui M.A.S.Z. , Al-Rufaie Y.A.
Published: December 2007

This paper reviews the effectiveness of three rigless techniques to reduce water production from oil wells that either produce excessive amount of water or become unproductible due to high water cut. Two techniques, setting a through-tubing bridge plug and plugging the water producing section with a cement plug have become standard procedures while the third technique, which involves pumping a polymer gel system in the reservoir, is still under testing and evaluation to determine its suitability in Saudi Arabian reservoirs. During the last two years, 42 water shut-off jobs were performed of which 35 jobs (83%) were successful in reducing water and increasing the oil production. Post-job water cut trends show that these jobs extend the productive life of the well by 1–2 years and have excellent payout prospects in terms of increased revenues from higher oil production and reducing water production, thereby reducing the associated water processing costs. From reservoir management point of view, these jobs help in maximizing recovery from areas of the reservoir that have been invaded by the advancing flood front.

P. 135
Challenges to Secondary and Tertiary Recovery Operations in Carbonate Reservoirs:
Authors: Lindsay R.F.
Published: December 2007

Carbonate reservoirs are inherently heterogeneous and challenging to secondary and tertiary recovery, due to:the depositional environment;the diagenesis that modified the sediment/rock;the nature of the enclosing trap; andthe properties of the fluids and gases that filled the reservoir.

Utilizing the above criteria when characterizing and managing carbonate reservoirs, from discovery to abandonment. gives an operating company opportunities to recover additional mobile oil (Fig. 1).

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A Development Project Case Study of the Virden-Daly Fields: Manitoba, Canada
Authors: Grant B.D. , Skow L.A. , Taylor W.J.
Published: December 2007

Virden and Daly are giant fields with mature waterfloods that have received minimal development attention since the waterfloods were initiated more than 30 years ago. An evaluation of the wells' production symptoms suggested that many areas within the fields were not optimized. Some areas display long, harmonic production declines with large remaining reserves. Other areas display injected water cycling through layers of high permeability while still other areas display a strong bottom-water drive that resulted in water coning. This paper describes a low-cost. short cycle-time method in which these fields were modeled and tested. A development pilot project was initiated to determine the economic viability of optimizing these fields. A conscious decision was made to accept a higher risk, but save time and money by designing a development pilot program directly from a conceptual. Streamtube displacement reservoir simulation. The 1996 pilot program consisted of 6 horizontal wells and 3 producer to injector conversions in areas of slow waterflood response, and in areas of water-cycling 3 polymer workovers on injectors were done to redirect water. Results suggested that the pilot program was an economic success. resulting in an expanded program for 1997 (9 horizontal wells, 5 conversions, and 1 polymer workover).

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Theory and Analysis Method of Pulse Testing for Responding Well in Buildup
Authors: Huang Bingguang , Li Shunchu , Liu Shuzhi , Zhai Huihai , Gan Zhenwei , Ma Hongmei
Published: December 2007

Pulse testing is an excellent technique used to determine the value and direction of reservoir permeability and other important parameters. When reservoir permeability is very low, however, the testing time that is designed by the conventional pulse testing theory may be more than two months. Its cause is that the pressure in many oil wells is still increasing when they have been shut in for more than thirty days. In view of the fact mentioned above, the authors developed a new theory and give interpretation method of pulse testing. The theory and method are suitable for responding well in buildup. In contrast, the conventional pulse testing theory is based on the fact that the pressure in the responding well must be stable. Consequently, it demands a much longer testing time than the new theory by the authors.

In the paper, a mathematical model is first established to describe the new pulse testing theory. with the wellbore storage coefficients and skin factors considered both in the responding well and in the pulsing well. Then, an exact solution to the mathematical model is derived in Laplace Space. According to non-linear regression analysis technique, the characteristic parameters of a reservoir are obtained by solving the objective function that is established by observed and calculated pressure. The theory has been applied to Shanshan reservoir pulse testing design and analysis for several times, the interpretation results are satisfactory, and the testing time is only 12 to 18 days in such reservoirs with low permeability as Shanshan. The actual application has shown that the new pulse testing theory and analysis method are practical. They can shorten the testing time, especially for low permeability reservoirs.

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Time Lapse Borax Logging in a Karstified Limestone Formation of the Panna Field,
Authors: Das Subhas C. , Fox Glenn A. , Zebrowitz Mark J.
Published: December 2007

Migration of undesirable fluids through cement channels behind the casing is frequently a cause of well productivity impairment. However, reliable identification of cement channels is difficult and, quite often, secondary cement squeeze jobs fail due to incorrect diagnosis of the existence, nature and extent of the channeling problem. Different techniques such as temperature profiling, radioactive tracer logging and activated water logging have been practiced in the industry, but the results are more often than not inconclusive. Borax logging has been used as an alternative method for detection of cement channels in sandstone reservoirs. The same technique has been applied in the limestone formation of the Panna Field located Bombay Offshore, India. The logging results are less definitive than for typical sandstone applications. However, with a proper understanding of the geological model, this detection technique can be effectively utilized as a cement channel identification tool.

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Use of New Horizontal Grids in Reservoir Simulation Models Improves the Chance of Success in Developing Marginal Thin Oil Rim Reservoirs using Horizontal Wells
Authors: Hsiu-Hsyong Hsu
Published: December 2007

This paper proposes an accurate method to represent horizontal wells in a reservoir simulation model. Conventionally, the model grids in the z-dimension coincide with the geological layers in order to honor the layer properties, resulting in non-horizontal corner point geometry grids. It is difficult to accurately place a horizontal well in this type of grids. At best it can be approximated by zigzagged segments within the model grids. This may create a serious problem in evaluating the application of horizontal wells in thin oil rims (35-65 feet). In this situation, the gas and water coning behaviors greatly affect the effectiveness of a horizontal well. A simulation model using zigzagged segments to represent a horizontal well often gives an un-reliable prediction because some segments may be misplaced toward the gas-oil contact while others toward the oil-water contact. This problem may become more acute in the assessment of a marginal field development where the expected productivity of a horizontal well may influence the economic outcome of the project. Therefore, a computer program has been written to "horizontalize" the z-grids while preserving the original reservoir volumes and permeabilities. Where there is a shale layer in the reservoir, the horizontal grids are adjusted such that the shape and location of the shale layer are precisely preserved. This is an important feature of the program in that the shale layer maintains its role as a barrier to the fluid flow. In this grid structure, non-neighbor connections of the model grids may occur; however, this can be handled by the reservoir simulator in use. The horizontal grids offer a number of advantages. First, a horizontal well can be accurately placed in the simulation model. Second, the optimal vertical position of a horizontal well in the oil rim can be meaningfully investigated. Third, the oil, gas and water rate profiles along the horizontal wellbore (from heel to toe) can be accurately predicted. This information is useful in the well completion design and in the planning of any flow control measures. This paper will present a benchmark study to illustrate the benefits of the horizontal grids and an application of these grids to the successful development of a UK North Sea field consisting of thin oil rim reservoirs.
Tracking Waterflood-Front Movement Using Production Logging and Cross-Correlating
Authors: Verma S.C. , Madhavan S. , Roy M.M. , Banerji S.
Published: December 2007

For many stratified limestone reservoirs, waterflooding through strategically placed injectors is a sound strategy for both pressure maintenance and increasing hydrocarbon recovery. Complications like heterogeneity, preferential depletion of layers and non-availability of suitable injector slots make this task difficult, and often leads to early and unexpected injection water breakthrough in some producers.

This paper basically deals with a part of the Bombay High field, with characteristics similar to the one described above. Production log interpretation was carried out on all the relevant injection and production wells in this area, and an attempt was made to understand the complex nature of the flood front movement at different points of time for individual layers. From the available log and core data on porosity and permeability in these distinct layers, a study was conducted to see if any cross-correlation can be made between the flood front movement and the reservoir parameters. Finally, the paper comments on whether such log and core deduced permeability data, which account for only a tiny fraction of the reservoir volume, is sufficient to predict water movement in other areas of the reservoir, based on data from surface testings and production logs.

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