bluuebunny/crossref_metadata_2025 huggingface dataset:
Skin Damage Removal Using Coiled-Tubing Vacuum: A Case Study in Venezuela's Orinoco Belt
Authors: Figueroa Jorge , Hibbeler Jeffrey , Duque Luis , Perdomo Lenin
Published: December 2007

The Orinoco Belt in Venezuela contains the largest known deposits of heavy oil in the world. Estimates for proven reserves are estimated to be 1.2 trillion barrels of oil-in-place (STOOIP) and the field covers an area of 5400000 hectares (54000 km2) across three states in Eastern Venezuela. Drilling in the area started in 1953 and over the years new technologies like horizontal drilling have made possible the economic exploitation of previously heavy oil plays. BITOR, a subsidiary of Petróleos de Venezuela S.A. (PDVSA), is an operator in the Cerro Negro field located near Morichal in Monagas State, Venezuela. Recently, Cerro Negro is developed only by horizontal wells, completed with a slotted liner / open hole horizontal. Over time the horizontal section has been increased to improve production, however this has also made it more difficult achieve a clean well. Conventional methods to remove filter cake and drilling fluids were not effective and caused downhole pump problems and formation damage.

Recently a new coiled tubing technique has been devised to clean wells by means of a hydraulic jet pump. The pump creates a pressure drop across the formation sandface and unwanted fluids, polymer residues and solids are transported to surface. This technique is ideally suited to horizontal heavy oil reservoirs where pressures are low and viscosity is high. The technique makes use of Concentric Coiled Tubing (CCT) and a special Vacuum Tool (VT) designed to apply a specific and controllable drawdown. Several jobs were performed on wells in the Cerro Negro with outstanding results. Post job analysis of vacuumed wells has revealed improved bottom hole flowing pressure and increased production compared to non-vacuumed wells. Moreover, analysis of fluid returns shows that significant amounts of polymer residue as well as both drilling and formation solids are being cleaned from the face of the completion.

This paper illustrates the usefulness of CCT vacuum technique and several complementary technologies now being applied. A comprehensive technical review and case study of work performed in the Cerro Negro field are also presented.
Horizontal Water Producers Increase Heavy-oil Recovery Factors
Authors: Boardman D. W. , Zerpa L. B.
Published: December 2007

Morichal-01 is a 9° API heavy oil field located in the Venezuelan Orinoco Heavy-Oil Belt. The reservoir comprises unconsolidated, Darcy permeability channel sands at a depth of 3-5000 ft, and contains a STOIIP of 8.7×109 stb. Development has been on-going since 1956 with a 2% recovery factor to date.

A history matched thermal numerical simulation model showed that recovery is unlikely to exceed 4% of STOIIP using conventional production methods, due to viscous fingering by the aquifer and artificial lift related production problems. Using the simulation model, the authors show that in a relatively undeveloped area of the reservoir close to the aquifer, placing horizontal wells to pump off the aquifer influx substantially reduces viscous fingering and sustained dry oil production can be achieved updip, increasing the recovery factor above 10%. Dry oil production is additionally expected to reduce emulsion problems and costs, improve pump efficiency and reduce disposal costs from uncontaminated produced water.
A Study of the Influence of Number of Components on Compositional Reservoir Simulation Results
Authors: Hildebrand M. A. , Liu K. , Mezzatesta A. G.
Published: December 2007

The number of components used in the compositional simulation of petroleum reservoirs affects both the accuracy and the speed of simulation results. A proprietary, fully automatic fluid characterization technology provides an efficient way to reduce the number of components of reservoir fluid samples used to simulate relevant laboratory tests within a predefined accuracy. This paper focuses on investigating how the number of components impacts the speed and accuracy of real world compositional reservoir simulations.

The procedure starts with using PVT laboratory test data to characterize the reservoir fluid behavior under anticipated reservoir production mechanisms. The PVT laboratory test data are matched within a given accuracy by running the proprietary Fully Automatic Reservoir Fluid Characterization package, where the minimum number of components can be set by the user. The characterized EOS parameters are directly exported to a compositional simulator to perform the actual reservoir simulation using different numbers of components and two different simulation schemes, i.e., IMPES and Fully Implicit. Simulations are performed for a range of fluid types, from volatile oils to gas condensates.

This paper presents a systematic investigation of how the number of components influences the accuracy of simulation results and the speed of the simulation. Three examples show that this method of reducing the number of components results in a significant increase in the compositional simulation speed while, at the same time, retaining the prediction accuracy.
Supply to a Commercial Network - Planning of Production
Authors: Manitta José Orlando , Di Cugno Carlos , Gaona Miguel Angel
Published: December 2007

The problems related to the supply of oil products to a commercial network are handled. It will be intended to approach these topics in a way that enables to visualize those aspects that have more weight, in order to build a scheme where the resulting costs have been optimized.

The first part of the papers deals with the way of setting up a scenario where the supply will take place, focusing on the planning of production as an alternative to all other remaining possibilities in order to fulfill the supply to a commercial network.

The demand of oil products appears as the basic information required in order to solve the problem, and the details of what this input must involve are given here. All potential alternatives that must compete to fulfill the supply, achieving concomitantly optimization, are also presented in detail.

The way of performing the optimization of logistics and distribution of oil products is detailed as a very important part of the scenario. A general framework that can be adapted to any company that sells products in bulk, independent of its particular features, is used. Work tools are mentioned, among which stands out a software that uses a mathematical model with linear equations and an objective function, that once minimized after running, gives the solutions that achieve economical optimization through minimum cost. This output found is the basis to build the advisable program of logistics and distribution for the period that is being planned.

The setting up of the scenario is completed by application of criteria to appraise oil products and raw materials, providing also some methodologies to keep track of margins of profit in order to envisage from the beginning the most likely behavior of the mathematical model for production programming.

Once the appropriate scenario is completed, the aspects related to programming of production are detailed. Obviously, work tools used are mentioned, and also those elements of major significance taken into account in designing a model for one or more refineries, such as ways of operation, severity of processes, slate of crude oils liable to be processed and their corresponding assays, finished products specifications, possibilities of blending from different streams, uses of additives in finished products, processing in plants of third parties or for third parties, etc.
Estimation of Fluid Properties Using NMR Correlations in Berea Rocks
Authors: Rodrigues Patricia , Romero Pedro
Published: December 2007

Fluid viscosity is one of the most important parameters necessary to establish reservoir production and economic potential. Until the appearance of Nuclear Magnetic Resonance (NMR) techniques in the oil industry, oil viscosity determination was limited to laboratory tests and correlations with API gravity. Nuclear Magnetic Resonance response is the consequence of fluid properties, as viscosity and density, and its interactions with its surroundings. In water wet rocks, oil NMR behavior depends only on its properties, since it has not contact with the pore surface. However, the water attached to the surface has an effect on the global NMR signal. The technique used to overcome this situation is the NMR differential spectrum, which consists in implementing two different polarization times during NMR measurements, one that polarizes all present fluids and the other, which only polarizes the water. This technique has shown good results for sand reservoirs saturated with light oil, since the polarization time of light oil is much greater than the polarization time of water in sandstone. However, this technique cannot be used with confidence, in presence of heavier oil or in rocks where the water has greater polarization time, since both signals can be overlapped. This study is based on the idea of generating correlations to determine fluid properties through the use of mixed NMR signals of oil and water. In the study, we used Berea rocks to determine correlations for API gravity and oil viscosity vs. logarithmic average and 1st quartile of the NMR T2 distribution, for three different echo times (300, 600 and 1200 μs). These correlations were determined in a general form as function of the echo time for free fluids and in saturated samples. API gravity correlations for free fluids and fluids inside the porous media showed similar results, while viscosity results showed the need of a specific correlation for fluids inside the porous media. This work constitutes a preliminary step on the generation of correlations to determine fluid properties inside the porous media.
Productive Innovations for Cementing Liners in Deep Wells
Authors: Valles C. , González O.
Published: December 2007

The objective of this paper is to highlight the results and experiences obtained by the Petroleum Company of Venezuela (PDVSA) as a result of the changes applied to the displacement systems in liners, for the cementing of intermediate and production strings in the deep wells of the North Monagas area, located in Eastern Venezuela.

In the year 1998, there was a 24% drop in the success rate of liner cementing during the well construction process. This resulted in the execution of 11 repair jobs having to be performed to correct primary cement job failures, with an associated cost of US $370,000. Based on an analysis of the execution and evaluation of the said jobs, it was determined that the most recurrent problems were flaws in the displacement system with the different types of hangers used. As a consequence, a more detailed analysis was done which allowed the identification of the most common causes when the failures occurred, such as: the piston effect between the liner displacement plug and the seal bore, and inadequate sealing during the latch-in of the plugs. As a result of the optimization proposals and changes made to the designs in liner hangers used for cementing 7 5/8 inch intermediate and 5 ½ inch production strings, a 22% increase in the success rate was achieved compared to 1998, thus reducing the percentage of repairs to primary cement jobs due to failures in the liner hanger to just one from a total of twenty seven (27) jobs performed in the period 1999–2000. By these changes, a total of US $1,500,000 in additional costs for repairs to primary cement jobs was avoided.
The Use of a Coarse Grid Simulation for History Matching and Development Planning, Quiriquire Deep Field
Authors: Zambrano H. , Rusinek I. , Jalfin G. , Lee Sheng-Tai , Muralidharan V. , Rigatti Vincent
Published: December 2007

The Quiriquire Deep Field located in the Eastern Venezuela is a large and complex compartmentalized accumulation, with a hydrocarbon column of some 3,500 ft. (3000 ft in the gas cap and 500 ft in the oil rim). The appraised part of the field has an estimated 2.0 TCF of Original Gas in Place both free and associated, and 550 MMBO (50 MMBO from the gas cap and 500 MMBO from the oil leg). There is a very significant variation with depth of the stock tank oil API and the standard gas/stock tank oil ratio within the fluid column both in the gas cap and the oil legs (>50 °API to <15 °API). The multidisciplinary study included a static numerical representation of the geological model, taking into account all available information and integrating the vertical communication among formations and the reservoir compartmentalization as inferred from the available performance/dynamic data (mainly pressures, production tests and fluid types). Given the very limited dynamic information available and the limitations of seismic imaging in this area, a History Matched coarse grid simulation model was used as a Material Balance tool to study reservoir compartmentalization; evaluate volumes in place per compartment; and estimate well counts and overall recoveries for alternative development scenarios. A key part of the model was an accurate representation of the complex PVT behavior, including depth profiles of oil content in the gas, oil API gravity and initial Rs; as well as GOC depth estimates for each compartment. The study supports the blowdown of the gas cap as the most commercially attractive and less risky development strategy.
Hyperspectral Imaging for Upstream and Downstream Operations
Authors: Prelat A. E. , Wieser J. D. , Gazzani R. O. , Re Kuhl G.
Published: December 2007

Hyperspectral remote sensing involves the collection of reflected and emitted solar energy from the earth's surface in a large number of bands or channels. Typically, this wavelength range extends from the ultraviolet (UV) through the visible (VIS), infrared (IR) and microwave regions of the electromagnetic spectrum. Since all exposed ground materials have a characteristic spectral response or "signature" to the incident radiation, hyperspectral imaging allows for more precise identification and evaluation of the targeted land cover.

Alto Technology Resources has developed an airborne hyperspectral imaging spectrometer that circumvents many of the problems associated with current sensors. This state-of-the-art scanner collects data in a very large number (>200) of channels throughout the UV, VIS and IR portions of the electromagnetic spectrum, taking special advantage of the thermal IR and an integrated synthetic aperture radar (SAR). This provides unparalleled spectral resolution and interpretation capabilities. All spectrometer band centers and bandwidths are selected for specific applications and the spectral data are fully calibrated. The system control uses an on-board workstation to provide real-time data monitoring and georeferencing. The imaging spectrometer is mounted on a fully stabilized platform. The recording system is flexible and expandable.

The Alto hyperspectral sensor has been successfully tested and used in several missions involving upstream and downstream operations. This paper briefly discusses the fundamentals of the various types of remote sensing and presents examples of the application of hyperspectral imaging in hydrocarbon exploration and exploitation operations. Among the upstream examples to be discussed include identification of structural traps and outcrop lithology and onshore and offshore oil seep detection. In downstream operations, it has been used to monitor an underground pipeline for hydrocarbon leaks, perform environmental assessments at refineries, pipelines and oilfields, monitor a remediation site and assist in pipeline routing.
Government and the Mineral Industries: Rationalizing the Relationship
Authors: Eads George C.
Published: December 2007

Any significant shortages that this Nation will face during the next quarter century — and probably for generations thereafter — will not be caused by finite limits on the quantity of resources within the earth's crusts or by our slowly growing dependence on overseas mineral sources but by short-run shocks that produce shifts in demand or supply large and abrupt enough to exceed the immediate adjustment capabilities of the materials-producing and materials using industries. While certain of these abrupt shifts lie outside human control, a surprisingly high proportion of them are likely to be related either directly or indirectly to the actions of governments our own included. Government policies have come to exert a major if not a dominant influence over key industry decisions at each stage of the materials cycle. It is critical that the Government take steps to improve its understanding of how its policies impact on industry so its influence policies impact on industry so its influence can be exerted in a constructive rather than a disruptive manner. The recommendations made by the National Commission on Supplies and Shortages are designed to help bring about such an improvement

There is a well known story about how to tell an optimist from a pessimist. Take a quart jar and put a pint of water into it. When shown this combination, the pessimist will remark, "Too bad, it's half pessimist will remark, "Too bad, it's half empty." The optimist will say, "oh good, it's half full."

Press coverage relating to our Commission's report has generally put us into the "oh good, it's half full" category. "World Resources Will Last, U.S. Panel Says," was the page l headline in the Los Angeles Times the day our report was released. "Resources Aren't Running Out, Report Says," was the headline on the January 16 Detroit News story describing our report.

I don't like to be the one responsible for throwing water on this sense of euphoria, but I do think it is important to put our findings and recommendations into proper perspective. This is what I hope to do today.

The National Commission on Supplies and Shortages was created in the wake of the first widespread period of commodity shortages since the Korean War.
An Examination of the Concept of Coverage in the Evaluation of Financing in the Extractive Industries
Authors: Andrews Horace , Everitt John W.
Published: December 2007

The cost of projects in the extractive industries has soared in recent years. At the same time companies are asking commercial banks to finance more of the total costs of the projects. Banks have been obliged to recognize projects. Banks have been obliged to recognize project financing as a special discipline and project financing as a special discipline and to augment their staff and use new techniques to analyze risk.

Lenders and equity owners evaluate project risks from different vantage points. project risks from different vantage points. This paper explores these differences by focusing on the concept of coverage as used by banks in evaluating risk. Coverage analysis is contrasted with rate of return analysis used by companies.

The general areas of risk in project financing are enumerated and several of these are discussed. Finally, this paper deals with the level of coverage that is acceptable to banks and why it is difficult to quantity. Coverage is a reference point from which a lender may make a judgment about a project's ability to service debt.

One of the most important economic restraints on the mineral industry is the ability to finance future capital requirements. We would like to focus our discussion on the nature of the financing needs and the process of evaluating financing proposals.

For a Perspective

The Bank has seen a change in the financing needs of natural resource companies. During the post war period up until the mid 1960's a large portion of the western world's mining capacity was financed by corporate entities. Although these mining projects were large rarely was a single project so large that it could damage a corporation's credit standing if it were not successful. Internally generated funds - that is, cash flow from operations - provided the major portion of the financing requirements. To the extent that there were external borrowings, they were predominantly for short-term working capital predominantly for short-term working capital needs.

Today's Financing Challenge

Today things are quite different in the extractive industries. The future capital requirements are huge. In 1974 Morgan Guaranty roughly estimated the capital required to develop the capacity needed to meet demand for the remainder of this century for a group of selected minerals. We projected that cumulative requirements could be as high as $750 billion for the western world, excluding capital needed to replace existing capacity. Perhaps more challenging for the mining companies than the aggregate investment is the fact that today individual projects are larger and more complex.
Downhole Upgrading Athabasca Tar Sand Bitumen Using THAI – SARA Analysis
Authors: Xia T. X. , Greaves M.
Published: December 2007

Downhole upgrading of virgin Athabasca Tar Sand bitumen has been investigatede in a series of 3-D experiments using THAI - ‘Toe-to-Heel Air Injection'. The process uses direct line drive, or a staggered arrangement of horizontal producer wells; in combination with either horizontal or vertical wells for gas injection (HIHP or VI2HP). The 3-D tests involved THAI as a primary process, steam injection aslo as a primary method using a new steam flood process, THSF (Toe-to-Heel steamflood), and THAI on a secondary recovery mode, post-THSF. Except for THSF, very high oil recoveries were achieved: THAI primary: 80% OOIP, THSF: 23% OOIP and THAI secondary: 66.7% OOIP. The low THSF recovery is attributed to the low steam temperature, because of the low cell opersting pressure. Very significant upgrading of the Athabasca bitumen occurred during the air injection tests for the majority of the experimental period. The API gravity of the produced oil increased by 8 API points and the viscosity decreased to 50 to 1000 mPa.s, compared with the original bitumen viscosity of 1,000,000 mPa.s. There was also a substantial decrease in sulphur, nitrogen and heavy metals content of the produced oil. The quality of the in-situ upgraded oil was investigated using SARA analysis (Saturates, Aromatics, Resins, Asphaltenes). This revealed that there was a dramatic increase in the saturates content of the produced oil, up to 62% to 72%, compared with 15.5% for the original bitumen.
Application of 2,000 Hydraulic Horsepower to Rotary Drilling
Authors: Watson Ralph A. , Sullins R.S.
Published: December 2007

Increases in pump hydraulic horsepower from 500 to over 1,500 have, with adequate bit weights, resulted in penetration rate improvements exceeding 100 per cent in drilling 12–1/4 and 8–5/8-in. holes in south Louisiana.

Indications are that further increases in drilling rates may be effected with pump output horsepower increased to 2,000. However, improved methods of generating cuttings are needed to take full advantage of the continuing trend of increasing available mud pump horsepower. For proper power utilization during deep drilling, operating surface pressures of 5,000 psi should accompany development of 2,000 pump horsepower. Drill pipe diameter should not be less than 5 in.

Although hydraulic horsepower increases benefit penetration rates with weighted muds as well as with muds of normal weight, loss of returns, more prevalent with heavier muds, may necessitate reduction in circulating rates and horsepower in some instances.

Introduction

During recent years drilling rates generally have been improved by the combination of increased bit weights and hydraulic horsepower used. Whilehard West Texas drilling, the benefits have been obtained from great increases in bit weight with lesser emphasis on more hydraulic horsepower, as formations become more drillable greater hydraulic horsepower increases are necessary to reap the improvements possible with increased bit weights.

Formations penetrated in South Louisiana are predominantly of soft material and can be drilled rapidly. In these formations, bit weights which can be carried are usually limited by the ability of the hydraulic system to keep the bottom of the hole and the bit clean and to remove bit cuttings from the hole. Although in the past, drilling rates with low hydraulic horsepower appeared to be adequate; recent experiments with greatly increased mud pump horsepower have shown that with adequate bit weight, penetration rates increase markedly.

To date increases in pump hydraulic horsepower from 500 to values approaching 1,600 have made possible penetration rate improvements exceeding 100 per cent in South Louisiana drilling in normal pressure areas. indications are that further increases in drilling rates may be effected with even greater hydraulic horsepower provided it can be properly utilized.

Discussion

As this paper is composed of [1] the theoretical application of 2,000 hydraulic horsepower to rotary drilling and [2] the actual field experiences in utilization of 1,500 and smaller hydraulic horsepower, the discussion has been divided in two parts.
Evaluation Of Gas Injection In The Fyzabad Syncline Field
Authors: Ramkissoon Martin B.
Published: December 2007

Partial maintenance of reservoir pressure through gas injection has been successful in the FS/LC/ 438/III Reservoir in the Gyzabad Syncline Field. This paper discusses the actual and predicted performances of paper discusses the actual and predicted performances of the reservoir.

The Fyzabad Syncline Field is one of the few cases of hydrocarbon accumulation in a Syncline. The reservoir is a sandstone matrix with highly variable characteristics. It is located at 7200 ft., subsea, and consists of four distinct sand beds the uppermost being the most extensive and comprises the gas cap.

Rapid decline from the initial reservoir pressure of 4915 psig coupled with the availability of produced gas, resulted in a gas injection program being undertaken to partially maintain reservoir pressure. On initiation of partially maintain reservoir pressure. On initiation of injection, the reservoir pressure had fallen to 2080 psia with a recovery of 27.4% of the original oil in place. Present reservoir pressure is 900 psia with a corresponding Present reservoir pressure is 900 psia with a corresponding recovery of 38.97% of the original oil in place.
Downhole Blowout Preventer
Authors: Andersen A. , Sivertsen A.
Published: December 2007

A downhole blowout preventer (DHBOP) for improved well control while drilling has been developed and tested. The tool is not meant to replace the traditional BOP, but to be an additional barrier when the mud is out of control. The tool is located in the bottom hole assembly. The wellbore can be sealed off in case of an influx or lost circulation. Mud of adequate density is circulated through the drillstring and into the annulus just above the downhole seal until wanted wellbore pressure is achieved. The field test has demonstrated the functions of the tool, but also identified needs for improvements. Tool modifications may also introduce additional functions like multi-operational circulation port, drillstring choke and test plug for traditional BOPs.
The Effects of Petroelum Production Operations on the Environment In Trinidad
Authors: Jaggernauth Deonarine D. J. , Seeram Basdeo
Published: December 2007

Trinidad is unique in its natural resources. Since the discovery of the first oil well, on land, in 1857 the country has seen an emergence of land operations in the petroleum industry. Drilling operations from 1902 to present continue to impact on the environment, but the adverse effects have been surpassed by production operations. Wells remain on production for many years and while initially they presented no threat to the environment, maintaining integrity of aging infrastructure is an increasing challenge. Leaks from wellheads, leaks from pipelines, and overflows at gathering stations, among others have contributed negatively on the terrestrial environment.

Petrotrin, a state owned company in Trinidad, which has several production operations throughout the south of the country, has inherited production operations and their liabilities from predecessor companies. Over the past few years and continuing into the future, a new approach has been taken in which a "win-win" situation has emerged and will continue to emerge. For example, in the area of wellhead and pipeline leaks, which have effluents from which weathered in the environment, rendering them chronically polluted sites, bioremediation is employed. To avoid leaks from corrosion, a preventative maintenance is in place. The basal sediments are being recovered from tanks and taken to a designated site for treatment and remediation. Case studies show the effect of a proper environmental management system on the current infrastructure and installations and the necessary steps being taken to prevent any adverse effect that production operations may have on the terrestrial environment.
An Integrated Safety and Enviroment Information System
Authors: Pereira Azevedo Miguel Francisco , Constantino Roberto , Maida Fernando
Published: December 2007

This paper presents the development criteria and implementation steps of a Corporate System of Information on Safety and Environment ("Sistema Corporativo de Informações de Segurança e Meio Ambiente" - SISIN) implemented in PETROBRAS-Petróleo Brasileiro S.A as a strategic management tool. The Systran in reference involves some 40 units, including main offices and operating units, encompassing a universe of 35,000 (May/2001) employees of the Company, almost 60,000 Contracted employees and totals 70,000 records approximately in the period from 1985 to 2001 (May), including records of accidents resulting in personal injuries and records of incidents.

The engineering adopted for the development of the data bank employed the concepts recommended in the ISO-9000 series Quality rules, with reference to a wider application of the definition of "non conformity". The criteria set forth in the Brazilian Standard of Accident Recordings NBR-14.280, issued by the Brazilian Technical Standards Association ("Associação Brasileira de Normas Técnicas"-ABNT) were also taken into consideration, as well as the international rules on which the charts included in the Systran were based.

The purpose of this paper is to evidence the managerial importance of an Information Systran of such dimensions, since the basic assumptions adopted for its development, such as the processing speed of data input, data availability in real time, concepts and national and international indicators were employed and are strategically necessary within a globalization scenario, in which information quality and productivity are increasingly needed elements, as well as fundamental factors of corporate survival.
Visualisation of Oil Recovery by Water Alternating Gas (WAG) Injection Using High Pressure Micromodels - Oil-Wet & Mixed-Wet Systems
Authors: Sohrabi M. , Tehrani D. H. , Danesh A. , Henderson G. D.
Published: December 2007

In reservoirs that have been waterflooded or gas injected, it is still possible to recover a significant amount of the remaining oil by water-alternating-gas (WAG) injection. WAG injection has been successfully implemented in some waterflooded reservoirs. However, the physical processes underlying the complex three-phase flow in WAG have not been well understood.

A series of WAG experiments has been conducted, using high-pressure glass micromodels, with high quality images of the oil recovery processes being video recorded. The experiments were performed using water-wet, oil-wet and mixed-wet micromodels. The authors presented the results of the experiments of water-wet models in SPE ATC&E 2000 (SPE 63000)1. This paper presents experimental results of oil-wet and mixed-wet models and demonstrates the difference in flow mechanisms of the WAG process under different wettability conditions.

Pore level fluid flow and distribution were studied and fluid saturations at different stages of the experiments were measured. The results showed that oil recovery was higher for WAG injection than for water or gas injection alone, under any of the wetting conditions. It was also observed that WAG recovery was higher for strongly oil-wet or mixed-wet models than for strongly water-wet one. Experimental results on water-wet models had highlighted the importance of corner filament flow of water in oil recovery process, with the initial water flood residual oil being trapped in the majority of pore space mainly surrounded by layers of water, and not in only large pores. The successive WAG cycles redistributed the fluids, creating fresh pathways for gas to enter the pores occupied by oil, hence, some of the oil which otherwise would not have been mobile under either gas or water injection alone was mobilised and produced. In a strongly oil-wet micromodel the flow resembled a piston type of displacement. The residual oil was only the amount staying in form of films on the pore surface, the filaments in the corners and some trapped in patches of pores surrounded by small throats. During gas injection following water injection, gas was observed to avoid entering most of the water-filled pores and preferentially invaded oil-filled pores. This is due to a much lower value of gas/oil interfacial tension than oil/water IFT. The mixed-wet model contained pores of varying degrees of wettability; from strongly water-wet and pores of intermediate wettability to strongly oil-wet pores. The displacement process in the mixed-wet model was a combination of those observed in the two extreme wettability conditions.
Field Performance of Propellant / Perforating Technologies to Enhance Placement of Proppant on High Risk Sand-Control Completions
Authors: Folse Kent C. , Dupont Richard L. , Coats Catherine G. , Nasse David B.
Published: December 2007

The combined use of propellants and perforating for production enhancement is not new to the petroleum industry, especially for natural completions in competent formations. When used together, the propellant is shaped in the form of a cylindrical sleeve that is positioned over a typical scalloped perforating carrier to combine the perforating and stimulation processes into one step. The perforating event is performed in either an under-balanced or balanced condition, followed immediately with the extreme over-balance or rapid-gas pulse generated from the propellant burn. This technique provides an effective method to ensure that all perforations are sufficiently broken down with the fracturing to accept either produced or injected fluids.

This paper will review a new application for the combined propellant / perforating technique that has been successfully used in unconsolidated formations in the Gulf of Mexico. The propellant / perforating technique was used to enhance the placement of proppant during frac-and-pack treatments while perforating in a balanced condition. The propellant / perforating technique was used on several formation types; i.e., long intervals, highly deviated, and highly laminated with extreme permeability contrasts, that would traditionally be deemed as high risk for proper sand placement. The propellant sleeves are positioned across the lower quality portions of the intervals with low permeability and resistivity to ensure that the perforations performed in these intervals are broken down to accept fracturing fluids and proppant during the fracturing treatment consistent with the entire treated interval.

Two case histories from a major gulf-of-Mexico operator will be presented and will discuss the steps that led this operator to use this propellant/perforating technique to overcome sand placement problems (screenouts).

In the case histories presented, it will be shown that that this technique is effective in both underbalanced and overbalanced perforating situations. With the trend in the industry to reduce cycle time, the elimination of the underbalance/surge process to ensure clean perforations and all the associated rig time in obtaining control of the well following the surge are seen as opportunities for rig-time savings. It has now been proven that combining propellant/perforating in a balanced scenario can also offer cost efficiency and safety when used as a near wellbore clean up tool for pre-frac preparation.
Extreme Overbalance Perforating and One-Trip Perforate and Gravel Pack-Combination of Two Techniques for Successful High Rate Gas Well Completions in the Ha'py Field
Authors: Vickery E. Harold , Hill Leo E. , Forgenie Victor , McCollin Roger , Fahmy Helmy , Butler Carl H. , Mohamed Omar Y.
Published: December 2007

The Extreme Overbalanced Perforating (EOB) technique has been successfully applied in a variety of locations around the world both in ‘hard rock’ and ‘soft rock’ formations. In certain applications, it offers definite advantages over other perforating techniques. One-Trip Perforating and Gravel Pack technology also has been successfully applied at various locations with definite advantages over other ‘soft rock’ cased hole completion techniques. Prior to the completion of three wells in the Ha'py field, these two technologies had never been applied concurrently.

This paper describes the teamwork that was required between the operating company and the service providers to properly combine these methods and ensure their successful application in the field. The authors outline some of the obstacles encountered and describe how the tools and procedures were designed for success.

During the three well completions in the Ha'py field, some problems were encountered that required modifications to operations. The lessons learned from these problems and how they were applied to subsequent operations are also addressed.
Simultaneous Gravel Packing and Filtercake Cleanup with Shunt Tubes in Open-Hole Completions: A Case History from the Gulf of Mexico
Authors: Godwin Keith , Gadiyar Bala , Riordan Hal
Published: December 2007

The cleanup of reservoir drill-in fluid filtercake presents a significant challenge in long open-hole gravel-packed completions. In an effort to prevent leak-off into the formation and ensure complete interval packing, it is advantageous to leave the filtercake in place during gravel-pack operations. A post gravel-pack breaker treatment is then performed to remove the filtercake. This treatment typically consists of a coiled tubing operation in which chemical breakers (enzymes or oxidizers) and/or acid systems are pumped to attack the polymeric and CaCO3 components of the filtercake. Acid treatments or two-stage enzyme /oxidizer soaks followed by acid can be ineffective in providing uniform cake removal and can result in substantial associated cleanup costs. Cake cleanup while gravel packing has recently been proposed to reduce an otherwise two or three-stage process to a single stage, thus eliminating the need for coiled tubing and ensuring breaker contact with the filtercake throughout the entire interval.

In this paper a case history from the Gulf of Mexico for drilling and completing a horizontal open-hole well utilizing simultaneous gravel-packing and cake-cleanup with the alternate path technique is presented. The open-hole section was 277 feet deviated from 85° to 90°. Bottom-hole static temperature was 128°F. The producing sand was normally pressured. The drill-in fluid and gravel-pack carrier / filtercake removal fluid selection was based upon extensive laboratory testing which consisted of clean-up, compatibility, and sand suspension capability tests. A reservoir drill-in fluid comprised of a brine, starch, a biopolymer, and sized calcium carbonate was chosen for the project. A viscoelastic surfactant fluid in a chelating-agent solution containing an enzyme breaker to simultaneously attack both the starch and the CaCO3 components of the filtercake was identified as the best carrier fluid for the gravel pack. Laboratory test results, field procedures, and the production results are discussed in detail along with the decision process that resulted in the selected drill and completion plan.
An Integrated Approach to Evaluation of Horizontal Completions in Panna Field: A Coning Dominated Heterogeneous Limestone Reservoir
Authors: Kak Suhail , Malik Sanjeev , Choudhuri Biswajit
Published: December 2007

The Panna field is a heterogeneous limestone reservoir consisting of a thin oil column overlain by a gas cap and underlain by a water column. The reservoir is coning dominated and the wells show a marked increase in Gas Oil Ratio (GOR) and water cut very early in the production history. Horizontal wells were drilled to minimize drawdown, and hence coning, and maximize recovery. The initial horizontals had openhole completions and displayed a peculiar inflow performance curve that was concave upwards and almost flat at the higher rates. This was thought to be caused by the formation of water sumps at low rates, due to the undulating profile of the drainhole & the low fluid velocities, which resulted in a non-uniform flow contribution along the horizontal. Subsequent wells were completed with a centralized, selectively perforated tubing (tailpipe) installed in the drainhole and it was thought that this would result in a uniform flow contribution along the entire horizontal section and correct the inflow performance curve shape. Analysis of pressure data from the tailpipe wells showed that the tailpipe caused progressively higher drawdown at high rates. However, the flow distribution along the drainhole could not be determined from pressure data alone. A production logging campaign utilizing tractor as the conveyance system had to be aborted due to a) limited coverage of the horizontal section by the tractor and b) operational problems resulting in fishing of the tractor in one of the wells. This campaign was expected to provide an insight into the flow process in the two completions and determine the most optimum one.

This case study presents the performance of the various horizontal completions in existence in the field and integrates production and bottom-hole pressure data to explain them.
The Carbon/Oxygen Log Measurement
Authors: Wichmann P.A. , Hopkinson E.C. , McWhirter V.C.
Published: December 2007

1978 Rocky Mountain Regional Cody Wyoming May 17–19, 1978

A new pulsed neutron logging technique has been developed to unambiguously identify the presence of the element carbon. The Carbon/Oxygen Log is currently available on a limited commercial basis in North America and has been tested under a wide variety of field conditions.

This paper covers the theory of the log's response and shows examples of what is available in the way of taped output. The basics of interpretation by a simplified pattern recognition technique are reviewed along with test pit measurements and verified field response. pit measurements and verified field response

Introduction

During the past three years, a Carbon/Oxygen logging device has been commercially available and has been used to survey several hundred wells. Despite the fact that a great many of these applications have been made as a "last resort" when definitive answers could not be derived from other more conventional logging methods, the device has scored a very high success ratio in predicting the type of fluid ultimately produced. Also complicating these initial efforts is the fact that development and improvement of the instrumentation has been continuous over this period of time and even now, a significant advance is on the verge of commercial introduction.

The Dresser Atlas Carbon/Oxygen Log is made possible by an electro-mechanical device that can be pulsed in extremely short, concentrated bursts of 14 Mev neutrons and a detector system that can selectively discriminate and count the high energy gamma rays that result from the inelastic collisions of these neutrons with the atoms of carbon and oxygen. Figure 1 schematically reviews the source and time frame of neutron bombardment induced gamma radiation. Note that the inelastic or prompt gamma rays exist only while the very high energy neutron source is on and for a very few microseconds following the cessation of the pulse. From this period of time until the neutron source is reactivated, only gamma rays of thermal neutron capture, and to a lesser degree, activation gamma rays, are present. This is an extremely important point, as the 4.43 Mev inelastic carbon gamma ray is the only unambiguous nuclear indicator of that element in nature.
Successful Gas Shut Off Using Latest Gel Technology In An Indian Offshore Carbonate Field — A Case Study
Authors: Sengupta T. K. , Singh Rudal , Avtar Ram , Singh Kharak
Published: December 2007

The offshore-A oil field is located in the Arabian Sea to the west of Mumbai India & is operated by ONGC under Asset based management system. The field is a saturated reservoir with three small gas caps & is under production with pressure maintenance by peripheral water injection. Some of the wells falling near to the gas cap produce with high GOR due to gas coning or cusping. Several efforts made to control the high gas production by conventional cement squeeze technique did not produce any result. As a result the wells were either closed or under production sub-optimally with a low choke size.

The low recovery from the area due to closure of the high GOR wells & unsuccessful attempt of cement squeeze jobs for Gas shut off warranted ONGC to search for new technology to control the high gas production with a deep penetration new gel technology.

Accordingly the gas control jobs were carried out in two wells after an extensive study on reservoir characteristics, selecting best candidate wells & right type of polymer gel, involving laboratory studies to see the compatibility of the gel with the core & formation fluids and using proper gel placement technique. This integrated approach with a multidisciplinary team effort was adopted for the first time under the asset based management system.

The post treatment production data showed significant reduction in total gas production along with substantial increase in oil production which indicates that the gas production from the gas cap has been blocked successfully by this treatment.

The paper deals in detail the integrated team approach adopted in the Asset team for a reservoir focussed conformance solution to improve the recovery which led to a success and has opened up a new era in the gel technology for gas shut off in carbonate reservoirs in Indian offshore fields.