bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental Management System Developments by the E&P Industry
Authors: Rost Susan T. , Hinds Aston A.
Published: December 2007

Executive Summary

Over the past 20 years the way in which the Exploration and Production (E&P) industry manages environmental affairs has changed dramatically. In the beginning, environmental was thought of something that would be taken care of concurrently as safety moved from program management to a management system approach. Currently, while a variety of methodologies exist for controlling the environmental impacts of E&P companies and support companies.

Implementation of HSE Management Systems is ranked as greatest area of progress over the past five years by the oil and gas industry according to the SPE 2006 HSE committee.1 Many of the majors and larger European Union (EU) E&P based corporations have Environmental Management Systems EMS combined with Health, Safety & Sustainability. There is a distinct difference in these disciplines where as safety is impact of safety hazard tend to be immediate and acute; where as Environmental impacts are sometime acute, if the event is large (a major oil spill), but usually develop over time; Health and Sustainability issues are more gradual to discover but very significant once they occur. Training and measuring environmental, health and sustainability programs and management systems is harder to do. Disparities in consistencies also exist between how integrated environmental programs are between upstream and downstream operations for of many Oil and Gas Producers.
Vibration and Rotation Considerations in Extending Coiled-Tubing Reach
Authors: Newman Kenneth R.
Published: December 2007

In recent years there has been increased usage of coiled tubing (CT) to drill1 shallow wells or to drill laterals from an existing wellbore. Often the weight on bit (WOB) which can be applied with CT is limited due to friction between the CT and the wellbore, preventing some drilling operations and methods from being possible. Two methods proposed to reduce this friction are vibration of the CT and rotation of the CT. This paper presents research that was performed to determine the effectiveness and practicality of these two methods.
Deployment of Advanced Collaborative Environments at Scale In The North Sea Operations
Authors: Phillips I. C. , Critchley C. , Shaw P. , Thomas J.
Published: December 2007

As part of its global FIELD OF THE FUTURE initiative, BP in the North Sea has embarked on a programme to significantly change how onshore and offshore staff interact and collaborate, with the objective of improving the efficiency of drilling and operations. This paper reports on the first phase of this project, in which five Advanced Collaborative Environments (ACEs) have been designed and deployed in the BP Aberdeen office in support of production operations. These environments take advantage of a range of digital technologies to deliver operational data to a wider team who are focused on further improving operational excellence.

The second phase of this programme involves the deployment of ACEs into all remaining North Sea assets as BP moves into its new offices in Aberdeen in late 2007 / early 2008.

The paper describes the following; The extensive consultation with the operational staff involved onshore and offshore to ensure that the new systems delivered meaningful support to the offshore operationsThe steps taken to ensure complete "ownership" of the new way of working, for both onshore and offshore teamsA review of the business benefits anticipated and/or achieved by this deploymentThe integrated hardware and software technologies deployed to deliver offshore data to an onshore support environment in real timeThe thinking behind the physical configuration of the onshore and offshore working environmentThe plans for the second phase of the project, in which further ACEs will be deployed across all BP's North Sea producing assets. This deployment will be the subject of a subsequent paper
Permeability and Relative Permeability Measurements at Reservoir Conditions for CO2-Water Systems in Ultralow-Permeability Confining Caprocks
Authors: Bennion D. Brant , Bachu Stefan
Published: December 2007

Carbon dioxide has been successfully used in more than 80 enhanced oil recovery (EOR) operations in North America, and the number of such operations may increase significantly around the world if CO2 becomes available at reasonable costs. On the other hand, geological storage in deep saline aquifers and hydrocarbon reservoirs of large amounts of CO2, captured from large stationary sources is one method that is under consideration for reducing greenhouse gas emissions into the atmosphere on a worldwide basis. In both cases of CO2-EOR and CO2 capture and geological storage (CCGS), the containment of CO2 within the injection unit and leakage avoidance are essential. Effective CO2 containment is achieved by the overlying tight caprock that is initially highly saturated with formation brine, which prevents CO2 migration into uphole intervals and potentially into shallow freshwater aquifers and ultimately to the atmosphere. The confining properties of the caprock are due to its very low permeability and to relative permeability and capillary pressure effects that prevent the penetration of CO2 into, and significant flow through the caprock. Essential to the assessment of CO2-EOR and CCGS operations, including numerical simulation, is knowledge about the caprock permeability to brine and CO2. This paper presents results of detailed measurements at full reservoir conditions for permeability to water, primary drainage and secondary imbibition permeability, relative permeability and trapped saturation of supercritical, dense-phase CO2 and brine for three different, regionally-extensive low permeability formations in the Alberta basin, Canada. These formations include Devonian and Cretaceous shales and a Devonian anhydrite whose measured relative permeabilities were found to be in the nano to pico Darcy range.

The methodology used in the test program and the results can be extended to the evaluation of other sealing caprocks for other prospective CO2-EOR or CCGS operations around the world.
An Integrated Modeling Approach for Characterizing Multiphase Flow, Chemical Transport, and Heat Transfer in Fractured Reservoirs
Authors: Wu Yu-Shu , Lu Guoping , Zhang Keni , Bodvarsson G. S.
Published: December 2007

Even with the significant progress made in modeling flow and transport in fractured rock in the last few decades, characterizing fractured reservoirs remains a great challenge. This is because of the inherent complexity within actual fractured reservoirs, from multiphase flow and transport to the spatial variability of the fracture network. To investigate coupled processes of fluid and heat flow and chemical isotopic transport in the highly heterogeneous, unsaturated fractured tuff of Yucca Mountain (a proposed underground repository site for storing U.S. high-level radioactive waste), we present an integrated modeling methodology. The proposed modeling approach integrates a wide variety of moisture, pneumatic, thermal, and geochemical isotopic field data into a comprehensive three-dimensional numerical model for modeling analyses. In particular, the results of this evaluation indicate that moisture data, such as water potential and liquid saturation in the rock matrix, are not sufficient to determine in situ percolation flux, whereas temperature and geochemical isotopic data provide better constraints to net infiltration rates and flow patterns. In addition, pneumatic data are found to be extremely valuable in estimating large-scale fracture permeability. The integration of hydrologic, pneumatic, temperature, and geochemical data into modeling analyses is thereby demonstrated to provide a practical modeling approach for characterizing flow and transport processes in complex fractured reservoirs.
Calculating Seismic Attributes Within a Reservoir Flow Simulator
Authors: Emerick Alexandre Anozé , de Moraes Rafael Jesus , Rodrigues José Roberto Pereira
Published: December 2007

This paper describes the implementation of a petroelastic model (PEM) based on Gassmann's equation to calculate seismic attributes into a commercial reservoir flow simulator. This implementation is the first step of a project to integrate time-lapse (4D) seismic attributes into an assisted history matching tool developed in a previous project.

The paper includes the description of the PEM and some implementation issues, such as the coupling of the model with the flow simulator with the purpose of using its basic calculated properties, discuss some user options (such as properties input through correlation or geoestatisticaly obtained maps) and the model variants and extensions (such as lithology influence and pressure effects). Three applications of this petroelastic model are shown: the first is a synthetic model based on outcrop data; the second is a 4D feasibility study for water injection monitoring in an offshore field; and the last one is a comparison between observed and calculated pressure impedances for an offshore field.

The resulting tool is applicable, for example, in 4D seismic feasibility studies, in seismic modeling for comparison with observed surveys and makes possible further implementations for incorporating the seismic data in assisted history matching.
General Fracture/Matrix Transfer Functions for Mixed-Wet Systems
Authors: Lu Huiyun , Blunt Martin J.
Published: December 2007

We extend a model of fracture/matrix transfer in dual porosity and dual permeability systems to mixed-wet media, where there can be displacement due to imbibition when the capillary pressure is positive combined with gravity drainage. This can lead to a characteristic recovery curve from the matrix, with a period of rapid imbibition followed by slower recovery as buoyancy overcomes capillary forces. We refine a current general transfer function model (Lu et al., 2006) to accommodate such cases by including transfer due to horizontal and vertical displacement separately.

The model is tested against fine-grid simulation in one and two dimensions and accurate predictions are made in all cases; in contrast the conventional Kazemi et al. (1976) model gives poor predictions of rate and ultimate recovery.
New PDC Technology Solves Hard/Abrasive-Formation Challenge Drilling Vertical/Directional/Horizontal Applications
Authors: Miller Clayton , Al-Jezany Mahdy , Balhareth Mahdi , Adebiyi Ismail , Klink Zeinoun , Parham Hoss , Butt Imran , Al-Abed Hussain
Published: December 2007

The operator has attempted to efficiently drill the 8-3/8, 5-7/8 sections using roller cone tungsten carbide inserts (TCI) and polycrystalline diamond compact (PDC). In the 8-3/8 5-7/8 sections abrasive wear caused by hard/sharp sandstone limited PDC life. Even the toughest cutter could not withstand the abrasivity. The operator required new cutter and PDC technology.

Engineers used numerical models to optimize the interface between the diamond table and substrate that determines the cutter's response to residual and service stresses. Diamond table properties were changed to increase durability and wear resistance. The result is an abrasion-resistant cutter capable of maintaining a sharp edge in hard carbonates and abrasive sands. Patented depth-of-cut control technology provided increased stability. Directionally drilling 8-3/8 section through hard/abrasive sandstone with 105pcf overbalanced mud is challenging. TCI, delivered poor ROP while sliding while wear resulted in short runs, lost cones, causing fishing/milling. PDC was tried previously in similar formations with minimal success (cutter wear). A baseline was set using three TCI with diamond enhancements which drilled 75ft in 36.5hrs, at average ROP of 2ft/hr (cost/ft $2240). Using the new cutter technology, four bits drilled 543ft in 116hrs at average ROP of 4.68 ft/hr at cost/ft $778. One bit drilled a record 279ft at 4.73ft/hr. The new PDC technology achieved 65% reduction in drilling cost, saving over $750,000 on one well by reducing drilling time and eliminating fishing operations

The 5-7/8" lateral is drilled through the abrasive Jauf reservoir. In the Hawiyah field, the new PDC technology drilled 1620ft of hard/abrasive sand using three bits. The first sidetrack, took nine roller cones and two PDCs to drill 1207ft. The cost/foot reduction was $283/ft for a total savings of $460,000 over this section. With improved cutter technology, a second well was drilled in the same field that required two PDCs to drill 2368ft at 16ft/hr. This performance set the lowest cost per foot horizontal section in this application.

In the 5-7/8" vertical application drilling the Unayzah formation in the Ghazal Field, new PDC technology drilled 517ft of hard abrasive formation using two bits, compared to the best offset for the same section using one impregnated bit and four TCI. The cost/foot reduction was $229/ft for a total savings of $118,000.
Variations in Structural Styles Across the Burgos Basin, Mexico
Authors: Rivas-Reyes Esmer Orlando , Ziga-Rodriguez Genaro , Martinez-Vasquez Trinidad , Norte Region , Goodoff Lynne R.
Published: December 2007

The Burgos Basin in northeastern Mexico as shown in Fig. 1 produces from the clastic Paleocene in the western portion of the basin to the Miocene in the east. Fig. 2 is a stratigraphic chart of the Tertiary. As different Tertiary formations exhibit different structural styles, the primary structural style of each major formation will be discussed and compared. Structural features across the Burgos Basin are not uniform, but complex. Interpretation on 2D and 3D seismic data, on both regional and field development scales, has revealed faults and structures that result not only from extensional forces, but also from compressional or transverse forces. The purpose of this paper is to give a general synopsis of many of the structural styles that have been observed in the Burgos Basin. A common perception that structuring in Burgos is similar to South Texas may limit a more complete understanding of the basin's true potential.

A majority of the faults are normal faults. Fault displacements range from a few meters to greater than 2000m (along the major growth fault systems). The extensional normal faults found in the basin have listric and high angle fault planes, syndepositional and post-depositional movement. Generally, synthetic faults are down-to-the-east and antithetic faults are down-to-the-west. Extensional structures include anticlines, synclines and graben systems.

While most of the structuring is consistent with traditional Gulf of Mexico basin extensional tectonics, faults with reverse throw, normal faults along which there has been subsequent reverse movement, and anticlinal folds have been observed. These features may be related to deformation occurring in the mountains to the west of the Burgos Basin and result from transverse movement that extends as far to the east as the border with the United States. These anomalous structures are strikingly visible on 3D seismic data. A northeast-southwest or northwest-southeast trend is observed in non-extensional faults and may influence producing trends through the formation of natural fracture systems.
Petroleum Facilities Reliability Assement Model
Authors: Palmieri Luis , Alonso Pablo , Moreno Adrián
Published: December 2007

The purpose of this paper is to create a calculation model to estimate the operation failure probability of an oil production facility, to guarantee an operation without accidents, without dangerous failures, observing the safety and environment policy established by the company. The facility operation is considered successful when it can carry out the functions it was design for.

Once the failure rate has been obtained, the system reliability level is obtained. The quantification of the success or failure is carried out through the application of the Failure Tree technique. The Safety and Operativity systems have been separately analyzed; taking into account that each of them has to be considered independently.

The model was used in the calculation of facility reliability in an oil field. (1)
Practical Interpretation of Pressure Tests of Hydraulically Fractured Wells in a Naturally Fractured Reservoir
Authors: Tiab Djebbar , Bettam Youcef
Published: December 2007

The main objective of this paper is to present a practical interpretation of the pressure behavior of a hydraulically fractured vertical well located in a naturally fractured reservoir. The interpretation is based on analytical equations derived to determine permeability, fracture storage capacity ratio, interporosity flow coefficient, skin and wellbore storage from the pressure derivative plot without using type-curve matching technique.

These parameters are obtained by making use of the characteristic lines and points found on the log-log plot of pressure and pressure derivative. The point of intersection of the straight lines corresponding to the different flow regimes are very useful in checking the parameters obtained from the slopes, when the pressure derivative curve is not smooth.

The method of analysis is applicable to both drawdown and buildup tests in uniform flux, infinite conductivity or finite conductivity hydraulic fracture. A step-by-step procedure and Examples are included to illustrate the proposed technique.
Sour-Well Serviceability of Higher-Strength Coiled Tubing
Authors: Luft H. B. , Padron T. , Kee E. , Szklarz E.
Published: December 2007

A joint industry project (JIP) among ExxonMobil Development Company, Shell Canada Limited and BJ Services Company Canada was initiated approximately 2 years ago to extend the prior research conducted into the serviceability of coiled tubing (CT) for under-balanced sour well drilling and work-over operations, to the higher strength (90 to 110 ksi SMYS) grades. A significantly different and unique laboratory testing protocol is employed in the present JIP research. The methodology entails full-body tubing specimens that have been immersed in a sour solution of varying severity followed by testing in a bend fatigue machine to determine the low cycle fatigue performance of high strength CT materials degraded by prior exposure to the sour environment. In addition, there are several important aspects of possible CT degradation from exposure to sour wells that were not adequately investigated previously. These include the incubation times for cracks to form due to hydrogen induced cracking (HIC) or sulphide stress cracking (SSC), the tensile strength integrity of coiled tubing strings in which HIC and/or SSC have formed, the relative resistance of different CT strength grades to HIC and SSC, the benefits of H2S corrosion inhibitors and the effects of different sour environment severities and external mechanical damage. Detailed metallographic examinations of the CT material characteristics that define their relative susceptibility to failure under sour conditions were also performed. Although the JIP research is still in progress, this presentation will reveal many of the significant results obtained to date with emphasis on CT operational implications and considerations. The newly obtained test results are also being exploited for the preparation of Alberta Industry Recommended Practices (IRP-21) currently under development in Canada.
Oriented Perforating Using Abrasive Fluids Through Coiled Tubing
Authors: Nakhwa A. D. , Loving S. W. , Ferguson A. , Shah S. N.
Published: December 2007

Abrasive fluids have been applied in mechanical cutting and perforating systems for years, the result is a precise cut in any size tubular. In abrasive perforating, the entry hole created reveals no tubular deformation or presence of flow obstructing debris. Consequently, the sand-laden fluid moves past cement, damaged zone or filter cake and into virgin formation. At that instant, velocity generated through the nozzles propagates abrasive fluid into multiple reservoir layers creating numerous pathways. Optimizing the direction of perforations allows for cost effective stimulation through conventional fracturing techniques. Therefore, as an alternative to conventional perforating, oriented abrasive perforating is applied specifically for creating channels to natural fractures.

This paper discusses the development of abrasive perforating coupled with orienting technology for penetrating tubing, casing, drill collars, and drill pipe, all of which is deployed using coiled tubing or jointed pipe in re-completions. In addition to conventional coiled tubing tools, this system utilizes an engineered weight bar connected to a high velocity perforating sub.

This paper begins with the development of this technology and existing perforating methods, then a description of tests conducted with the abrasive perforator and subsequent results. Benefits and applications with applied case histories are also discussed including multiple stage plug setting and perforating as well as pipe recovery, followed by conclusions and recommendations.
Case Histories of Barium Sulfate Scale Removal in Offshore Wells, Brazil, Using a New Engineered Combination of Coiled-Tubing Tools
Authors: Guimaraes Z. , Franca A. B. , Duque L. H. , DéSouza R. B. , Porto M. , Neves D. , Peixoto C.
Published: December 2007

With today's oil and gas prices, the loss of well production creates a negative financial impact on operating companies, especially in an offshore environment.

One of the most common reasons for production loss is the development of scales inside the production strings, blocking the flow of the reservoir fluid to the surface facilities. Barium Sulfate (BaSO4) scale is among the toughest scales to remove, whether mechanically or chemically. Alternatives to remediate this problem are often quite costly.

Therefore, under this scenario, a cost-effective intervention mechanism to restore production to previous levels is imperative. One of these mechanisms is the deployment of coiled tubing intervention as it can be done while the well is still live, minimizing further loss of production.

The Namorado field in Campos Basin, offshore Brazil, has approximately 60 wells, with most of them presenting deposition of BaSO4 scale throughout their production history. Historically, in this field, the deployment of a down hole motor with coiled tubing has been effective, but limited to restoring the production path's diameter only to the outer diameter of the bit. Results with deploying a down hole motor have been satisfactory. On the other hand, chemical treatments have been extremely ineffective and are, therefore, seldom deployed.

This paper presents two case histories of successful Barium Sulfate scale removal from the production tubing by coiled tubing, utilizing a combination of mechanical and hydraulic tools. This process is different from the conventional method (downhole motor) as it provides faster cleanout rates and quicker production restoration. This combination is engineered through software that optimizes the velocity at which the coiled tubing string is run through the scale, as well as the configuration of the hydraulic tool with respect to the pump rate and selection of the jet angle.
Measuring CT and Slickline Fatigue Life Reduction Due to Corrosion
Authors: Newman Kenneth R.
Published: December 2007

Coiled tubing (CT) bending fatigue has been the subject of much research. Slickline (SL) fatigue is the subject of more recent, ongoing research. Fatigue life tracking and prediction systems are available for both CT and SL. However, these systems do not adequately include the reduction in life due to corrosion. This paper discusses the CT and SL fatigue, and presents a new approach to handling the life reduction due to corrosion.
Successful Implementation of Coiled-Tubing Acid Tunneling Gives Operator a Viable Alternative to Conventional Stimulation Techniques in Carbonate Reservoirs
Authors: Diaz Jose Daniel , Espina Victor , Guerrero Melvi , Colmenares Omar Gregorio , Moss Paul John
Published: December 2007

Conventional stimulation techniques used to treat double porosity type (low permeability / hairline fracture) carbonate formations are met with limited success where most regular acid fracture treatments yield approximately the same results as regular matrix acid treatments of a much smaller scale.

This paper outlines the details & results pertaining to some recent successful applications of a new technique whereby Coiled Tubing is used to create multiple, relatively short-length lateral holes into a carbonate reservoir using nothing but hydrochloric acid pumped through a specially designed jetting assembly. The discussed jobs were the first ever field applications of Coiled Tubing "Acid Tunneling" and the results showed one operator that this method represents a viable alternative to conventional stimulation treatments in said reservoirs.

Results indicate that this technique may be applied to all carbonate reservoirs, regardless of their inherent petrophysical properties, where a different approach to stimulation treatments is required.

Discussed are formation characteristics, acid volumes and strengths, job parameters witnessed, tools used and results obtained to date.

Field and Formation Characteristics

It is estimated that carbonate formations account for approximately 35% of the world's petroleum reservoirs yet these same reservoirs are estimated to contain about 60–70% of the world's traditional hydrocarbon reserves. Important carbonate reservoirs are found in most parts of the world with some notable ones being located in Sumatra, Borneo, China, Brazil and Venezuela. Carbonate rocks are typically low porosity/low permeability and naturally fractured, but offer two particularly useful but often-overlooked properties: mechanical integrity and high solubility in acids. Typical solubility of carbonates in hydrochloric acid is greater than 95% and often exceeds 99.5%.

The Mara field in Western Venezuela (Northwest Maracaibo Basin) is one of these petroleum producing areas that contain massive carbonate formations. This field presently has about 400 wells, of which 95 are actively being produced by means of Electric Submersible Pumps (ESP) and/or Progressive Cavity Pumps (PCP) and all of these wells are produced from the Cogollo lower Cretaceous group (95% Carbonates with a variety of micro fractures), which is comprised of the following formations:Maraca: Glauconitic and calcareous clays at the base of the formation with bioclastic massive limestone accounting for the upper portions of the zone.Lisure: Glauconitic clays, glauconitic sandy limestone with traces of shale.Apon: Black bituminous laminar limestone.
Coiled-Tubing Milling of an Incoloy Alloy 925 Safety Valve Flapper in the North Sea
Authors: Farquhar R. A. , Rattray F. A. , Annandale A. , Reid A. , Glegg S.
Published: December 2007

The Incoloy Alloy 925 flapper from a damaged tubing retrievable safety valve (TRSV) was blown downhole using a wireline conveyed cannon. A downhole video survey revealed the flapper to be deformed but intact, lodged above a PBR at 11,902 ft md RKB. Attempts to fish the flapper were unsuccessful and a CT milling operation was planned to reduce the size of the flapper to facilitate its recovery. Consideration of the material properties and the location of the fish indicated that milling could be challenging. Reported industry experience of similar operations was sparse and BHA selection and job design required very close co-operation between the operator, coil tubing and through tubing services providers. The flapper was successfully milled using a combination of crushed carbide and fine diamond grit dressed burning shoes and recovered with an alligator grab on slickline. In addition to presenting the case history of the operation this paper will give an overview of the planning and design considerations which contributed to a successful outcome. The paper will also demonstrate how extensive use of downhole video helped guide development of the intervention programme.
Improving Reliability and Consistency in BHA Configuration Through the Use of an Expert Tool-Selection System
Authors: Greenaway Robert , Burgos Rex , Dilling Lambert , Vreeland Cabe , Bruce Steve , Hauglund Loren
Published: December 2007

In an environment of high activity, large organizational growth, and the nearing of retirement age for a large proportion of the oil and gas industrial workforce (otherwise known as the "big crew change"), there is a high demand for experienced personnel to be correctly placed within an organization to bring maximum benefit for continued growth and knowledge transfer.

For a business organization to ensure its success during this challenging period, it must optimize its human capital in a way that will reap the most benefit. Part of this process includes capturing the experienced generation's design knowledge and passing it on in a way that maintains consistency and yet allows the experienced personnel to focus on more business-critical decision making or operational supervisory roles.

Configuring the bottomhole assembly (BHA) is typically a crucial point when preparing for well intervention using coiled tubing. Several strategies have been adopted by service providers to standardize and regulate the design stage and ensure continuity through the "big crew change," including: Providing intensive training and mentoring to act as a rapid handover between the experienced and the new generation of tool specialists.Creating and distributing fixed flow chart decision trees throughout the organization.Setting up a specialized group of experienced tool specialists that can be used as a geographically-mobile workforce that services the organization's global needs.Creating a dynamic technology-based computer system that captures the existing field design knowledge and also captures new lessons learned.

This paper discusses these strategies, examining the positives and negatives of each approach, and then goes into further detail of how a leading coiled tubing service provider has decided to handle this issue.
Opportunities for Rigless CT Intervention for Marginal Fields in Offshore Nigeria
Authors: Uadiale Victor E. , Asedegbega Daniel
Published: December 2007

Offshore well intervention with coiled tubing (CT) in the Niger Delta has traditionally been rig-based. Experience has shown this type of activity to have high cost implication both cash wise as well as in time. With the current focus on development of offshore marginal fields, it has become imperative to perform well intervention operations at a more reduced cost to the operator.

Non-rig based interventions can provide an economic advantage. However, inadequate facilities on existing offshore platforms and jackets present additional challenges. Furthermore, performing well intervention from a supply vessel is definitely not a mean task. Despite the complexity of this type of activity, the cost savings for not mobilizing a rig usually makes small intervention work that would increase oil production attractive to operators from the standpoint of ROI, vis-à-vis comparing the cost of the total intervention to the projected production gains. To the smaller operators and marginal field developers, this opens up a world of opportunities.

This paper explores these opportunities and discusses how they are being exploited to yield optimum benefit for the marginal producer. The success of carrying out various types of well intervention work on four wells (two dual completions and two single completions) is showcased as case histories.
Coiled-Tubing-Conveyed Perforating for High-Pressure/High-Temperature Environment in Mexico Marine
Authors: Molero Nestor , Garcia Sergio , Zavala Eduardo , Cordova Javier , Solis Ulises
Published: December 2007

In the Bay of Campeche, Mexico Marine operators have recently commenced the development of their high pressure, high temperature (HPHT) oil and gas fields in order to meet the high demand. These new developments present tough conditions for all aspects of well drilling and completion activities. They are particularly challenging for performing well intervention, which have driven operators, manufacturing and service companies to develop innovative strategies for servicing these fields.

For HPHT well developments, electric line conveyed guns is the most common technique employed to perforate wells in the area, whether dynamic or static conditions. Nevertheless, coiled tubing (CT) deployed perforating has been recently employed as a reliable option in the following cases: Electric line is not a technically suitable option due to the limited magnitude of under-balance at which it can safely operate.Drag and buoyancy forces encountered in the wellbore are close to the operational limits of the cable.Wellbore tortuosity, tubular restrictions and well configuration render electric line unable to access perforation target depth.

Initially, this paper discusses the workflow for performing technical analysis to develop safe and economical CT conveyed perforating operations for HPHT wells in offshore Mexico, which considers CT string design, surface equipment, well control equipment and associated downhole tools. It then presents case histories and lessons learned. And finally, provides conclusions and recommendations from the experiences gained for performing HPHT CT deployed perforating activities in Mexico Marine.
A Novel Coiled-Tubing Wall Thickness and Ovality Measuring Tool for Field Use
Authors: Standen Robert , Pike Don
Published: December 2007

Some clients of coiled tubing service companies increasingly demand inspection of the tubing immediately prior to or during field operations. There is a lack of suitable available equipment for inspection of tubing for wall thickness and ovality deficiencies, particularly where operation in potentially explosive atmospheres is required.

Technologies exist for the inspection of wall thickness and ovality in both maintenance facilities and on operational locations but are commercially available only as a third party service; only one such service is known to be certified for explosive atmosphere use and all require trained technicians.

This paper presents a new wall thickness and ovality measuring tool engineered for reliable field use and which needs no specialist inspection personnel. By combining custom-designed fiber-optical transducers and magnetic flux leakage (MFL) principles, electrical apparatus is eliminated from the explosive area and certification is not required. The unique fiber-optic system design contributes significantly to the ruggedness and reliability of the inspection system.

Performance data from field service will be presented.
Estimation of Saturation Height Function Using Capillary Pressure by Different Approaches
Authors: Jamiolahmady Mahmound , Sohrabi Mehran , Tafat Mohammed
Published: December 2007

The saturation-height function greatly impacts reserve calculations and is used by geologists or reservoir engineers to predict the saturation in the reservoir for a given height above the free water level. If cores are preserved, the water saturation information can be obtained directly. However, cores are often subject to changes from their original state before brought to laboratories. Hence, capillary pressure (Pc) curves measured on different core samples of a heterogeneous formation are usually correlated to porosity, permeability, and/or rock type using various techniques to generate field wide saturation height function.

This paper evaluates performance of six saturation-height methods (i.e., Leverret-J[1], Cap-Log[2], Johnson[3], Cuddy et al. [4], Skelt-Harrison[5] and Sodena[6] methods) employed in the oil industry.

Measured capillary pressure data and core properties for a well in one of the North Sea reservoirs were used with rock permeability varying from less than 1 mD to over 1000 mD. We have reviewed advantages and disadvantages of each method while comparing the output of each method with saturation obtained from the log data. The results indicated that Skelt-Harson method with coefficient independent of core properties, a simple average Pc function, could be the best option and complicating the functional form by including the porosity and/or permeability data might inversely impact the predictions. Furthermore, modifying Cap-Log Cuddy et al. and kelt-Harison by including the core permeability data in the mutli-regressione exercise resulted in higher errors confirming that increasing the degree of freedom does not necessarily mean a better performance.
Faster Seismic History Matching in a UKCS Reservoir
Authors: Stephen Karl D. , Shams Asghar , MacBeth Colin
Published: December 2007

In seismic history matching, we perform a computer assisted history match to conventional production data but also include the spatio-temporal information offered by time-lapse (4D) seismic to further constrain the model. Good predictive models can only be found with a suitable search of the space of uncertain parameters such as permeability, porosity, net:gross and fault transmissibility.

We present a method of history matching that speeds up the search process. By using streamlines in place of a finite difference simulator, a factor ten speed up in simulation can be obtained. The model accuracy is slightly diminished affecting both the predicted well data along with saturations and pressures that are used to predict the 4D signal. We show how to reduce any bias effects by calibrating the model error and including it in the misfit calculation.

The method has been applied to the UKCS Nelson field using six years of production history and two seismic surveys. The field is maintained above bubble point and is ideal for streamline simulation. We compare the use of the finite difference simulator with the streamline method in history matching when we change net:gross and vertical permeability properties. By addressing the mismatch in seismic data together with production, we improve our predictive capability.

A proper parameter search increases the reliability of predictions made using simulations, and has great benefits for reservoir management. Decisions regarding water and gas handling, well maintenance and optimisation of production can be made with greater confidence and new wells can be planned with reduced risk.
History Matching Using Local Gradual Deformation
Authors: Gervais V. , Gautier Y. , Le Ravalec M. , Roggero F.
Published: December 2007

The gradual deformation method (GDM) is a geostatistical parameterization technique that generates a sequence of realizations evolving smoothly while preserving the statistical characteristics of the model. Combined with an optimization algorithm, it enables to constrain 3-D reservoir models to both static data (log data, prior geological information…) and dynamic data (production data such as pressure or water cut at wells…).

The gradual deformation is based on the weighted combination of several realizations using deformation parameters. It can thus be applied both globally, with the same deformation parameters for the entire domain, or locally. In this case, the domain is partitioned into non-overlapping subregions and each of these areas is attributed one or several deformation parameters independent from the other region parameters. This method, called local GDM, is more flexible than the global one. It can have several applications such as the integration of new data to improve the reservoir model, or the simultaneous deformation of regions with different geological properties or dynamic behaviors. An application of this method for history matching on a real data set is proposed in this paper.

One major issue when using local deformations is the definition of the reservoir partitions. Several approaches are considered in this paper, mainly based on the characterization of drainage areas and on geometrical criteria using Voronoi diagrams.
History Matching 4D Seismic Data with Efficient Gradient Based Methods
Authors: Emerick Alexandre Anozé , de Moraes Rafael Jesus , Rodrigues José Roberto Pereira
Published: December 2007

Time-lapse seismic is an important subject in the Petroleum Industry. Going beyond the qualitative interpretation of the seismic data, including quantitative information in the flow simulation model updating process, is a highly desirable goal. 4D seismic data give information far away from the wells, potentially allowing much richer parameterizations of the reservoir model in the history matching process. Since these parameterizations tend to be described by a large number of parameters, efficient algorithms are needed to tackle these problems.

This paper describes some efforts to integrate time-lapse seismic attributes into a derivative-based assisted history matching tool developed in a previous project1. The implementation of the seismic attributes derivatives using the forward and the adjoint method into a commercial reservoir flow simulator is described. The calculated derivatives are used in an optimization algorithm based on a trust-region Quasi-Newton method to minimize the mismatch between observed and simulated data from production and seismic.

Good results were obtained in several synthetic cases adjusting seismic and production data.
Tracking the State and Diagnosing Downhole Permanent Sensors in Intelligent-Well Completions With Artificial Neural Network
Authors: Aggrey G. H. , Davies D. R.
Published: December 2007

Permanent downhole sensors are extensively used in Intelligent Well completions. Typically, their numbers increase with the number of controllable zones. Replacement of a failed sensor rarely occurs in practice even when data is known to be incorrect (or completely missing) due to the cost implication of a workover. However, these sensors serve as the optic nerve for achieving the vision of Real Time Optimization. They measure parameters of interest (Monitoring) which is the first stage of the production optimization loop frequently known as "Measure, Analyze and Control", which will manage the reservoir and well performance. The reliability of permanent downhole gauges is not 100% throughout the well life. It is therefore imperative to authenticate whenever possible, the operational state of these downhole sensors. Such authentication will allows greater confidence to be placed in the data they supply.

This paper discusses how authentication is achieved by comparing the soft (computed) sensor value predicted by an Artificial Intelligence technique with the actual hard data. This approach is demonstrated using a real case data. An Artificial Neural Network (ANN) is trained with multi-dimensional historical downhole data. The ANN is shown to be able to validate continued proper sensor operation or diagnose a future malfunction of any sensor. It will also be shown that the trained ANN can predict parameters such as the zonal BHP, with sufficient accuracy and that they serve as back up to maintain reservoir management operations.
Detailed Special Core Analysis Program: A Key to Aggressive Field Development Planning—Rajasthan, India
Authors: Beliveau Dennis
Published: December 2007

In 2004, several large oil discoveries were made in high-permeability multi-layered Fatehgarh sandstone reservoirs in Rajasthan, India. The fields contain light but viscous paraffinic oils with wax appearance temperatures very close to reservoir temperature. As these were the first Fatehgarh discoveries in the region, no special core analysis (SCAL) information existed for the unusual oil-bearing rocks. A fast-track comprehensive SCAL program to determine wettability, relative permeabilities, capillary pressures, and initial and residual oil saturation was implemented within weeks of the first discovery. This data was critical to the design of waterflood patterns and facilities for these intermediate- to weakly oil-wet reservoirs.

The value of a comprehensive up-front SCAL program is clearly demonstrated. Although acquisition of the SCAL data cost ~US$5million, it played a crucial role in justifying a change in field development plans involving closer well spacing, higher injection volumes and larger surface facilities.

A statistically significant number of SCAL measurements were made on representative Fatehgarh samples. In general, reservoir rocks have the low initial water saturations (Swi~5%), long oil drainage tails and low residual oil saturations (Sorw<15%) typical of intermediate- to weakly oil-wet reservoirs (Amott-Harvey wettability index −0.33 ± 0.27). Early quantification of these characteristics by facies and their implementation into stochastic static and dynamic reservoir models were critical to development of a technically sound field development plan.

The 2004 discoveries in an industrially less-developed part of India are projected to be on production by 2009. Large fast-tracked investments in infrastructure and oilfield development were significantly shaped by the early acquisition of a comprehensive SCAL dataset. The data helped to optimize the different waterflood designs chosen for the different fields (pattern floods vs. edge line drives, well spacings, vertical vs. horizontal wells, etc.) and to quantify the expected oil and water production profiles from these very high-quality intermediate- to weakly oil-wet reservoirs.
Free-Fall Gravity Drainage in Fractured Matrix Blocks: Experimental and Network Modeling Simulation Findings and Observations
Authors: Mollaei Alireza , Haghighi M. , Maini B.
Published: December 2007

Free Fall Gravity Drainage as an important recovery mechanism was investigated and analyzed experimentally and by numerical (network model) simulation.

Sets of glass micromodels with real pattern of porous media and two numerical network model simulators were prepared in forms of fractured and non-fractured models to study and analyze the Free Fall Gravity Drainage recovery mechanism experimentally and by simulation. After validating the network model simulator, analysis of experimental and simulation results leads to some interesting findings and observations as follow:

Based on network modeling simulation, direction of flow through fracture network shows that the oil in the middle horizontal fracture usually flows from one end of fracture to the other end, however in relatively small fracture apertures the oil from both vertical fractures at the ends of middle horizontal fracture flows into the horizontal fracture and then sinks downward to the lower matrix block. This means in relatively small fracture apertures, block to block interaction coefficient (α) reaches to 100%. Another point is that, it was observed from network model simulation data that this critical fracture aperture is a function of pore and throat sizes.

Also, experimental and simulation results confirm that there is no break through of gas in free fall gravity drainage process. In addition a new mathematical approach (by means of flow potential and control volume concepts) to block to block interaction effects (Capillary Continuity and Reinfiltration phenomena) is presented to explain and interpret the mechanism of occurrence of these phenomena. This approach proves mathematically that decreasing the fracture aperture leads to increasing the fracture capillary pressure which in turn intensifies the feeding rate of liquid bridge (in the middle horizontal fracture) from upper block and lowers the discharging rate of liquid bridge from lower matrix block. Therefore, the liquid bridge can be more stable between the matrix blocks. As a result, fracture capillary pressure has positive effect on oil recovery from matrix blocks.

Finally, a new approach for determination of the matrix block threshold heights at the end of free fall gravity drainage is presented and used to prove that matrix block threshold height inreases with increasing the matrix block height. Also, it will be proved that matrix block recovery factor increases with increasing the matrix block height although matrix block threshold height increases too.