bluuebunny/crossref_metadata_2025 huggingface dataset:
Management of Occupational Health Offshore: Still a Challenge for the Industry?
Authors: Gardner R. J. , Wiig H.
Published: December 2007

Although little is known about the costs of work-related ill-health in the offshore sector, experience elsewhere suggests that these could be considerable. Yet occupational health has been recognized as a "poor relation" offshore compared with safety. The various reasons for this are discussed. An important feature is that data is needed in a form which not only convinces management of the need to take occupational health issues more seriously, but also allows them to develop performance indicators to measure how well they are doing. The available information and data suggests that musculoskeletal disorders and dermatitis are of particular concern offshore. Also the potential for problems from noise induced hearing loss and vibration white finger are high. Some areas of the management of prevention of work-related ill-health offshore which need attention are discussed and some performance indicators against which success may be measured are suggested.
Mapping Reservoir Saturation with Seismic Resolution to Improve Reservoir Model
Authors: Reymond S. B. , Soenneland L. , Strudley A.
Published: December 2007

Improved oil recovery on mature fields relies on a reservoir model accurate enough to identify by-passed oil and to monitor fluid responses to production. Integration of seismic 3D volumes with stochastic realisations and flow simulations in a single interpretation environment (Shared Earth Model) allows asset teams to perform rapid seamless iterations leading to a perfected representation of the reservoir (Fig. 1). Facies, fault and fluid mapping from 3D/4D/4C seismic data has moved one large step ahead with the advent of grid-based and 3D volume seismic classification (Fig. 2). Resulting deterministic spatial probability estimates of reservoir parameters are direct inputs to the reservoir model to constrain large uncertainties present in geostatistical distribution of reservoir parameters.
Seismically Guided Bypassed Oil Identification in A Mature Steamflood Area, Duri Field, Sumatra, Indonesia
Authors: Sigit R. , Satriana D. , Peifer J. P. , Linawati A.
Published: December 2007

The first large project area under steamflood at Duri field, Area 1, has recently been ramped down to the maintenance steam injection rate. After 14 years of steaming, Area 1 has achieved a recovery factor of about 64%. The available generated steam for this area, aside from the maintenance steam, is now being used to initiate new area development.

In 1996, the first 3D seismic survey in this area was acquired in the Southwest portion of Area 1 covering 33 patterns. This 3D seismic survey was aimed as a pilot project to identify the potential bypassed oil. The presence of the steam in the reservoir has changed the seismic velocity, distorted the seismic energy and lowered the frequency content. These factors have therefore lowered the seismic resolution to be able to resolve every injected flow unit. Vertical seismic profiles (VSP) have been heavily utilized as control data to interpret the flow unit boundaries and the faults. As a result, two major flow units (Pertama and Kedua-Baji Jaga units) were interpreted with confidence. Seismic attributes were extracted from these flow units. Pore fluid characterization was done using multi-variate statistical technique from the extracted seismic attributes to obtain the most reasonable steam saturation and bypassed oil maps which match the engineering data and production history. It was found that the bypassed oil regions were mostly controlled by both the stratigraphic and faulting systems.

A re-development strategy was generated by a multi functional team to recover the remaining oil. Seismic data was used to guide the interpretation of bypassed oil in areas not immediately adjacent to observation wells. This strategy consists of:

Selective zone re-injection Pattern re-alignment including well conversion and infill injectors Infill vertical and horizontal producer wells.

A target of about 4.6 MMBO of bypassed oil was identified in the study area. The approach used in this study has potential application in other areas in the Duri field that are in the earlier stages of the steamflood process. This would enable to recover of the oil as early as possible in the potential bypassed regions.
A New Numerically Model of Single Well Radial Multiphase Flow In Naturally Fracture Reservoir System, Using Fractal Concept
Authors: Dyah Rini R , Kana J. C. , Abdassah Doddy , Mucharam Leksono , Sucahyo W. P.
Published: December 2007

A new numerical simulation of single well reservoir model with fractal concept has been successfully developed in this study. The mathematical equations in which fractal dimension is explicity included have been formulated numerically for the radial three-phase flow (oil, gas and water) using a cylindrical coordinate system. By these new formulations, a radial multiphase flow in naturally fracture reservoir was modeled by assuming that all storage capacity in the rock system is merely due to fractures. The formulations of this model were then solved numerically by implementing the IMPES solution technique.

The model developed had been validated with the analytical model of single phase flow in radial system developed by Aprilian (SPE # 26465, 1993). In all cases, comparisons of these two models had shown similar results.

Using this new model, reservoir performance prediction of single well reservoir models had been performed with various cases and fractal dimensions. In this particular cases, the resulting performances of several hypothetical reservoirs with various fractal dimensions were then correlated to generate new type curve models. These type curves can be used for estimating fractal dimension of a reservoir.
A New Method for Designing 3D Trajectory in Sidetracking Horizontal Wells Under Multi-constraints
Authors: Shengzong Jiang , Xilu Wang , Limin Cao , Kunfang Liu
Published: December 2007

This paper proposes a new method for designing 3D trajectory in sidetracking horizontal wells based on optimization theories, in which some factors such as kickoff point, performances of bent housing motors, and tool-face angles etc. are considered quantitatively. The validation of this method is shown by more than 10 case histories. Comparison with conventional methods, the new method can greatly simplify the design process, generate more smooth curves with less length and can hit the predetermined point or target with higher accuracy.
New Experimental Approaches in Minimum Miscibility Pressure (MMP) Determination
Authors: Kechut Nor Idah , Zain Zahidah Md. , Ahmad Noraini , Ibrahim DM Anwar Raja DM
Published: December 2007

Miscible CO2 gas injection has nowadays become one of the most important enhanced oil recovery (EOR) processes. For optimal displacement efficiency, CO2 flooding should be conducted at pressures greater than a minimum miscibility pressure (MMP), which is a function of temperature and composition of injection gas. The MMP has been defined as the minimum pressure at which the injected gas and the oil become miscible with each other. Approaching miscibility, the interfacial tension (IFT) between phases decreases resulting in decreased residual oil saturation, hence, higher oil recovery efficiency.

This paper presents two new experimental approaches to determine the MMP for the miscible CO2 gas injection. The first approach consists of measuring the interfacial tension (IFT) between the injected gas and the oil at reservoir temperature and varying pressures using a prototype Vapour Liquid Equilibrium-Interfacial Tension (VLE-IT) equipment. The miscibility of the injected gas and the oil is evaluated on the basis of the vanishing IFT between the two phases.

The second experimental approach involves the MMP determination by displacement test using a prototype Gas Extraction & Miscibility Analyser (GEMA)*. The invention incorporates a capillary-sized unpacked column or a micro-slim tube (MST) as opposed to the conventional packed slim-tube widely reported in literature. The MMP analysis time reduces up to one tenth of the conventional slim tube or sand-pack flood.

It is demonstrated in this study that the approaches are reliable and fast for determining CO2 MMPs. The IFT method yields the quantitative information and the IFT MMP obtained is verified by the micro-slim tube displacement tests. The MMP obtained also falls within the range of values predicted by published correlations.
Petrophysical Properties of Sandstones Under True Triaxial Stresses I: Directional Transport Characteristics and Pore Volume Change
Authors: Al-Harthy S. S. , Jing X. D. , Marsden J. R. , Dennis J. W.
Published: December 2007

Transport properties are important parameters in controlling reservoir performance, and an understanding of how fluids flow through a reservoir can aid successful management of hydrocarbon recovery. Traditional laboratory measurements of permeability and resistivity are carried out in one direction which does not take into account any anisotropy in the rock properties. Furthermore, laboratory measurements of these properties are often carried out under conditions of equivalent hydrostatic stress, or sometimes anisotropic triaxial loading in which two of the principal stresses are equal. However, permeability and resistivity may vary in the three principal directions, and pore volume change may differ under different stress paths.

A novel method for measuring directional permeability and resistivity on a cubic sample under realistic true triaxial stresses has been developed and used in this study. This paper presents laboratory measurements of directional permeability, directional resistivity and pore volume change under conditions of hydrostatic and true triaxial stresses. Measurements of permeability and resistivity were carried out in the three principal directions using cubic rock samples of outcrop and reservoir sandstones. The main objectives of the work was to investigate directional and stress dependence of transport properties under realistic true triaxial stresses.

Results have shown greater pore volume change to occur under comparable hydrostatic compared to true triaxial stresses. The samples with laminations showed high degrees of anisotropy in permeability and resistivity under conditions of hydrostatic and true triaxial stresses. The degree of anisotropy was found to be constant between low and high stress. The permeability values were found to be higher under true triaxial stresses than under their corresponding equivalent hydrostatic stresses, whilst resistivity showed little differences. Thus the results have shown the importance of measuring directional transport properties and pore volume changes under realistic stress conditions.
New Air Injection Technology for IOR Operations in Light and Heavy Oil Reservoirs
Authors: Greaves M. , Ren S. R. , Xia T. X.
Published: December 2007

A new air injection technique, low temperature oxidation (LTO) process for residual light oil recovery, is described. Improved oil recovery from deep, light oil reservoirs is achieved by removing the oxygen in the injected air by LTO reactions with the residual oil in the reservoir. The product of the LTO reactions is a "flue gas", which displaces the oil. Preliminary results of LTO reaction kinetics and oil recovery have been obtained using four North Sea light oils.

THAI - "Toe-to-Heel" Air Injection, is a new EOR process, which integrates advanced reservoir technology and horizontal well concepts, to achieve potentially very high recovery of heavy oil. It can also realise very substantial in situ upgrading by thermal cracking, producing upgraded oil to the surface. The process operates in a gravity stabilised manner by restricting drainage to a narrow mobile zone. This causes the flow of mobilised fluids to enter directly into the exposed section of a horizontal production well. The process can be operated on primary production, as a new technology, as a follow-up to existing technologies, or as a co-process where the advantages of high thermal efficiency are required. This is achieved by concentrating the energy required for oil mobilisation, recovery and thermal upgrading in the reservoir.

Combined with clean technology design, THAI offers a pathway to future economic success for the heavy oil industry.
Enhance Oil Production in High Waxy Oil Reservoir by Single Well Cyclic Microbial Injection-Production
Authors: Chen Wei , Miao Mingcai , Chen Ling , Wan Dexin
Published: December 2007

The Sha 3 reservoir of Zhuangxi oil field is characterized by low permeabilityjhigh waxy oil and high reservoir temperature (92~115°C). The wax content of the crude oil is 18~46%, and its your point reaches 21~53 °C. Wax deposition results in various troubles, so that the producers can not work continuously, and the oil production and oil recovery is very low. In order to improve the oil recovery, the cyclic microbial injection-production testing was conducted in 10 wells. Two kinds of microbe were used. One is for controlling the wax, and the other is for treating the gum and bitumen. The preliminary result is satisfactory. Observation includes reduction of wax content and pour point and increment of oil production and light components of the crude oil. As a result, the power consumption and troubles decreased obviously. This paper introduces the well selection.field tests, observations and the results.
Hysteresis in Dielectric Properties of Fluid-Saturated Porous Media
Authors: Nguyen Buu-Long , Bruining Johannes , Slob Evert C.
Published: December 2007

We present in this paper the results of measurements of the complex dielectric permittivity and electric conductivity in three different porous media, made from unconsolidated acid-purified quartz sand and glass grains. To ensure the generality of the results, we use sand and glass grains of different geometry and particle size distribution. The measurements are made in the frequency range of 300kHz-3GHz, which covers the operating frequencies of all electromagnetic tools.

We have made measurements in a specially designed capillary pressure cell with a built-in transmission line which goes through the porous media. The measured capillary pressure curves serve as an indication of the capillary hysteresis during the entire drainage and imbibition cycle. From the scattering characteristics of the built-in transmission line, we computed the complex dielectric permittivity of the porous media as function of frequency and water saturation.

We obtained different values of complex dielectric permittivity and electric conductivity at the same water saturation during drainage and imbibition. At water saturation lower than approx. 0.6 the values of permittivity for the imbibition is lower than those for the drainage. At higher water saturation, the picture is the other way around.
Well Test Analysis for Multiphase Displacement Reservoir
Authors: Yin Hongjun , Zhai Yunfang , Fu Chunquan , Ma Shuilong , Li Zhongchen
Published: December 2007

In tertiary-recovery projects, kinds of measure are adopted to enhance oil recovery. One of them is alternate gas and water injection. After this measure, the displacement fluid in the reservoir becomes a gas-liquid mixture. Well test analysis for such multiphase displacement reservoir is still difficult.

In this paper, a mathematical model of the composite reservoir is established. The dimensionless wellbore pressure drop is solved analytically by using the Laplace transformation with numerical inversion. The corresponding type curves for appropriating injection/producing well are given. Moreover, the numerical solution is obtained by numerical simulation that considers effect of saturation distribution. By combining numerical method with analytical method, the inner and outer region mobility, skin factor, wellbore storage constant and front radius can be determined. Together with field examples, the paper analyzes pressure transient data of injection well and producing well.
Selected Indonesian Microbes Potentials For MEOR
Authors: Kadarwati Sri , Udiharto M. , Hadi Noegroho , Doria Indria
Published: December 2007

Oil recovery can be increased through the activities of microbes in a process known as Microbial Enhanced Oil Recovery (MEOR). MEOR technology has been implemented in a number of oil producing companies and has proven to have good prospect, environmental friendly and low cost.

The microbes which proliferate in Indonesia oil fields should be subjected to laboratory identification. Samples of formation water, oil, and soil were taken from various oil fields. These oil fields were selected on account of their reservoir temperatures which promise optimum growth of microbes. In order that MEOR can be applied in these oil fields, the microbes existing in their oil wells were isolated and identified.

Based on the results of isolation and identification activities several indigenous bacteria species were obtained from the oil well environment. The potential of each bacteria species for use in MEOR process depends on their ability to live and grow in the reservoir environment as well as the bioproducts produced, such as biosurfactant, bioacid, and biosolvent. The bioproducts produced depend on the inherent capability of the isolate as well as the support of the medium and environmental condition.

From the tests of their capability to grow in hydrocarbons, and live in semianaerobic condition, 12 isolates, were selected and some isolates were found to produce such bioproducts. The selected microbes and nutrient have been experimented by using microbial core flooding apparatus. The result has good prospect for implementation in the oil field.
Intelligent Systems Can Design Optimum Fracturing Jobs
Authors: Mohaghegh Shahab , Popa Andrei , Ameri Sam
Published: December 2007

Many computer software programs have been developed to assist petroleum engineers and scientists in designing hydraulic fractures. These programs use analytical, numerical or empirical methods (or a combination of two or all three methods) to model fracture propagation in the reservoir. The user - which is usually experienced petroleum professional - provides the necessary input parameters to the model. These input parameters include reservoir characteristics, fluid and proppant characteristics and treatment schedule. Usually among the major outputs of these models are the fracture geometry and conductivity.

The goal of this study is to provide a tool that allows the engineer to solve the inverse problem in a fast and efficient manner. Using the tool developed in this study the engineer identifies the desired fracture geometry that she/he would like to achieve and enters this value along with the reservoir characteristics into the intelligent software tool. The software tool would then solve the inverse problem and provides the engineer with fluid, proppant and the treatment schedule that would produce the desired fracture in that particular reservoir.

This new tool has been tested and shows to be capable of designing hydraulic fractures replicating those designed by expert engineers. An innovative hybridization of two virtual intelligence paradigms has been used to develop the methodology that is being introduced in this paper. An industry standard three-dimensional fracturing model (FRACPRO) has been used as the data set generator for the study.
Tight Sand Evaluation Applied to the Medina Group of Chautauqua County, NY
Authors: Pekot Lawrence J. , Wozniak David A. , Martin John P.
Published: December 2007

A systematic evaluation of the Medina Group in Chautauqua County, New York was performed in 1998 to identify production and reserve improvement opportunities in this large, continuous, low permeability gas accumulation. Petrophysical analysis, geological mapping and advanced production type curve analysis was performed over a 200 well study area covering 38,000 acres. Net pay, net sand and hydrocarbon pore-feet was determined from the log analysis. Structure, isopach, pay thickness, gas in place, permeability and well drainage areas were mapped.

Several infill/stepout locations were identified based on geologic parameter mapping and four new wells were drilled in the fall of 1998. Medina pay was encountered in agreement with the geologic prognosis for the wells. However, pore pressure was below original conditions indicating partial depletion at the new locations. Weekly production data was collected from the new wells for a six month period and decline curve analysis performed to estimate recovery.
Reducing the Cost of Field-Scale Log Analysis Using Virtual Intelligence Techniques
Authors: Mohaghegh Shahab , Popa Andrei , Koperna George , Hill David
Published: December 2007

One of the costliest parts of field-scale reservoir studies is log analysis. A recent GRI project required a detailed study of a field with hundreds of wells. As part of this study all the well logs were to be analyzed by an engineer in order to identify net pay, porosity, and saturation. It soon became apparent that a considerable amount of time must be devoted to well log analysis in order to obtain consistent and high quality reservoir characteristics throughout the field. This was mainly due to the fact that logs for several wells were missing and many wells did not have the suite of logs that were necessary for analysis.

This paper presents a novel approach to reduce the cost of well log analysis while maintaining the quality of the analysis. The cost reduction is achieved by analyzing only a group of the wells in the field. Using the detailed analysis of this group of the well logs by an expert engineer, an intelligent software tool is built to learn and reproduce the analyzing capabilities of the engineer on the remaining wells.

This approach provides a means to increase the efficiency of the engineering team. It can decrease the time needed to analyze a large number of well logs while considerably reducing the project cost to the operator. It will provide means to attain well log analysis for wells that do not have all the necessary logs needed for the analysis. This is achieved by generating virtual wireline logs for these wells. Virtual intelligence techniques are used in construction of the intelligent software tool presented in this study.
Infill Drilling Recovery Models for Carbonate Reservoirs - A Multiple Statistical, Non-Parametric Regression, and Neural Network Approach
Authors: B. R. Soto , Wu C. H. , Bubela A. M.
Published: December 2007

We used multiple mathematical techniques to develop primary ultimate oil recovery (PRUR), initial waterflooding ultimate oil recovery (IWUR), and infill drilling ultimate oil recovery (IDUR) models for carbonate reservoirs in West Texas. These are (1) non-linear regresion, (2) non-parametric regression (a statistical approach that constructs the functional relationship between dependent and independent variables, without bias towards a particular model), and (3) neural network models. Development of the oil recovery forecast models help understand the relative importance of dominant reservoir characteristics and operational variables, reproduce recoveries for units included in the database, and forecast recoveries for possible new units in similar geological setting.

One of the challenges in this research was to identify the dominant and the optimum number of independent variables. The variables is large including porosity, permeability, water saturation, depth, area, net thickness, gross thicknees, formation volume factor, pressure, viscosity, API gravity, number of wells in initial waterflooding, number of wells for primary recovery, number of infill wells over the initial waterflooding, PRUR, IWUR, and IDUR. The limited number of field data (43 data) points) are inexact and often exhibit uncertain relationships. We used an intelligence software1 that integrates multivariate statistical and neural networks to develop accurate neural network models. Multivariate principal component analysis is used to identify the dominant and the optimum number of independent variables. We compared the results from neural network models with the non-parametric approach. The advantage of the non-parametric regression is easy to use and the disadvantage is retaining a large variance of forecast results for a particular data set.

Develop a neural network model that is an "accurate" representation of data may be and ardous task that require experience with the qualitative effects of the structural parameters of neural network models. The advantage of neural network PRUR, IWUR, and IDUR models are capable of forecasting the oil recovery with less error variance.
The Evaluation of Aerial Surveys for Detection of Natural Gas Pipeline Leaks
Authors: Aminian K. , Chamorro A. , Ameri S. , Bilgesu H. I.
Published: December 2007

Pipeline leaks are of major concern to natural gas industry. They can result in loss of revenue, potential danger to public, and environmental damage. To ensure pipeline safety and reliability, a ground surveillance program to detect leaks is conducted on annual basis. Considering the number of miles of natural gas pipeline, this method is time consuming and expensive. There has been interest in developing other methods for rapid survey of natural gas pipelines. The visual aerial surveys, which rely on the identification of dead vegetation to detect a leak source, have a very limited application. The use of infrared technology to detect a leak based on thermal differences between the leaked pipeline gas and surrounding area has not been developed to the point to be reliable. An effective aerial pipeline leak detection system has been developed recently. The system utilizes an aircraft, which is equipped with flame ionization hydrocarbon detector. The hydrocarbon detector can analyze the samples taken during the flight over the pipeline right-of-way. Presence of natural gas anomalies, that are larger than natural gas background levels, represent a potential leak source. The accuracy and reliability of the aerial surveys however remains questionable. This paper reports the results of the both modeling studies and field tests conducted to evaluate the accuracy and reliability of the aerial surveys.

Buoyant plume rise and dispersion has been studied extensively because it is the primary mechanism for dispersing stack gases to the environment. A jet plume model that predicts the trajectory and dilution of vertically oriented gas jet was considered for this study. The model was then modified to develop user-friendly (Windows-based) input and output interfaces. The plume rise model was then utilized for sensitivity analysis in order to design a field test. The modeling results were utilized to determine the optimum flight plan. A pipeline leak was simulated by release of the natural gas during the field test. The model predictions were compared to the measured gas concentration to evaluate the predictability of the model. The measured gas concentrations were generally found to be in agreement with the predicted values. The results indicated that model can be used for the design of the flight plan and the analysis of the field data.
Viscosity and Thermal Conductivity Prediction for Hydrocarbon Systems
Authors: Erdogmus M. , Adewumi M. A.
Published: December 2007

Accurate prediction of thermophysical properties of gas- condensate systems is very important for optimum design and operation of most equipment involved in production, transportation, and processing of gas-condensate systems. The need for accurate prediction methods for these properties is inevitable because it is almost impossible to obtain thermophysical property data for every fluid that would be encountered. In addition, obtaining all of these properties via experimental procedures is not only time-consuming but also extremely expensive. Viscosity and thermal conductivity are such properties. In this study, a new technique using Enskog dense-gas theory coupled with an equation of state is developed to predict viscosity and thermal conductivity of gas-condensate systems. Ten different equations of state are used and extensive comparisons with experimental data are made over wide temperature and pressure ranges both for pure components and mixtures. The comparison with experimental data is good for both viscosity and thermal conductivity.
Developing Competence-Based Learning in Oman's Drilling and Well Services Sector
Authors: Davidson Ian A , Ali Al-Hashmi Khamis Bin , Al Zadjali Isam
Published: December 2007

To fully benefit from their natural resources Gulf states need to develop the skills of their indigenous populations and employ them at all levels in industry. Competence based learning is a means to effectively develop a competent workforce comprised of individuals who can consistently perform work activities to the standards required of the industry. The drilling and well service sector, through the efforts of the International Association of Drilling Contractors (IADC) and the Offshore Petroleum Industry Training Organization (OPITO), amongst others, is developing standards that are appropriate to the Gulf region.

This paper discusses some of the hurdles facing the implementation of competence-based learning and the optimum development of the national workforce. It concludes with recommendations for the way forward and highlights the potential benefits, to Governments, National Oil Companies and drilling and well service sector companies, of initiating competence based learning both at the workplace and in their training programmes.
Spectral Gamma Ray Measurement on Cuttings: An Alternative to MWD
Authors: Alixant JL , Collie D. A. L.
Published: December 2007

Conventional mud logging techniques cannot reliably distinguish the organic-rich, micro-porous Athel silicilyte reservoir cuttings from shale. Yet, a simple gamma ray log resolves most uncertainties in this respect. Spectral Gamma Ray logging on cuttings was introduced in South Oman in 1995 as a practical and cost effective means to optimise operational decisions on Athel wells. Target applications included picking casing setting depth, selecting coring points, and confirming TD. Equipment was designed and constructed, procedures were created, and personnel were trained. The "Cuttings Spectral Gamma Ray" has since become an integral component of the mud logging suite on many exploration wells in South Oman. In this environment, the technique proves technically and economically more attractive than alternative solutions involving wireline or MWD logging.

The original objectives were met, and new applications evolved as experience and confidence in the system grew. They include: depth-matching mud logs to wireline logs; correcting driller's depth; logging to the deepest point in the well; data assurance in case of hole problems; logging after completion or abandonment (where cuttings have been stored); and, in hindsight, a qualitative hole cleaning efficiency indicator. The paper reviews design considerations, operating procedures, and aspects of data processing. Using field data and comparisons with wireline logs, the discussion then focuses on current capabilities and inherent limitations of the system, to conclude with a brief assessment of the potential for a cuttings-based wellsite formation evaluation package.
Core Data Acquisition – An Alternative Approach
Authors: McKay A. M. , Moore T. A.
Published: December 2007

An ongoing requirement exists in the hydrocarbon industry to reduce the cost of wells and improve results when obtaining core samples. To achieve this objective in an already competitive market requires radical thinking. The result is a new and novel method of core acquisition, the SCORE system, which takes a continuous 7.62m (25ft) 36.5mm (1.44") diameter core from the sidewall of a well at an angle of 2° to the well trajectory. The tool comprises an inner coring assembly and an outer whipstock assembly run on standard API drill pipe. The whipstock section can be run as the bit for a wiper trip, thus technically eliminating all requirements for conventional tripping to acquire core samples. Additionally, the ability to log a well prior to any decision to cut core can produce significant savings in time and resources utilised in coring dry wells.
Downtime Reduction With Updated Maintenance System
Authors: Khelifi Mahmoud
Published: December 2007

The company is involved in drilling and workover activities and has currently 28 rigs operating in both Onshore & Offshore locations. Due to the large number and variety of equipment, formulation of a maintenance strategy to cater for the maintenance needs of all the above has become very complex. Initially jobs were done on a monthly basis & involved a lot of paper work and clerical time. There was no reliable means of automatically or manually updating the job completion hence a need was felt to have a computerised Preventive maintenance system.

With the formulation of the Maintenance Strategy in 1994, it was decided to go in for an optimum mix of Preventive, Predictive and Breakdown maintenance aiming to achieve equilibrium between them. As part of the Preventive maintenance exercise the company installed a computerised maintenance program designed to cover most of the equipment on the rigs. The same was installed on all the rigs in August 1996. As part of the Predictive maintenance exercise, procedures for overhaul/inspection of equipment were developed. Condition monitoring tools were introduced and some already in force were extended to cover more equipment. To minimise breakdown time standard repair workscope, overhaul procedures & spare parts lists were developed. To ensure that the workforce was geared to meet any eventuality, in-house training programs have been designed and personnel have been sent on specialised training programs so as to enhance the skill and know-how of latest maintenance techniques.

These measures have resulted in significant improvement in equipment availability and decreases in mean time between overhauls. Downtime for engines has reduced by 35.5% and in the case of Hoisting & Rotating equipment it has reduced by 33.97% as compared to the year 1994. In the case of Electrical, BOP & Controls & Mud system the downtime has reduced by 83.9%, 84.9% & 70.7 % resp. as compared to the average downtime in the year 1994.
Optimizing High-Temperature Kill Pills: The Åsgard Experience
Authors: Svoboda Charlie
Published: December 2007

Historically, the survival rate for conventional non-damaging polymer/carbonate kill pills under elevated temperatures was limited. Accordingly, a development program was instituted to develop a new high-temperature kill pill that would possess superb bridging characteristics on a high permeability proppant while remaining thermally stable at temperatures exceeding 165ºC.

This paper describes the development of a sodium formate kill pill geared specifically for the demanding Åsgard Development in the Norwegian North Sea. The pill was engineered and successfully applied in a high-temperature application to seal a high permeability (400-500 Darcys) frac pack sand in the Smørbukk field. In the field, the newly engineered formate-base pill proved to be thermally stable, while providing sufficient leak-off control. Furthermore, the development reinforced the critical role of proper particle size distribution in minimizing fluid invasion and formation damage.

With emphasis on particle size distribution, the authors will review the formation damage testing procedure of the new formulation on simulated frac packs. In the laboratory, the fluids demonstrated excellent thermal stability after long-term exposure to temperatures exceeding 150°C. After the pills were aged for 16 and 72 hours, leak-off tests were performed on 16/30 proppant at 165ºC, resulting in minimal filtration. The authors also will examine the unusually demanding conditions at Åsgard relative to other Norwegian fields and will detail the application and performance of the new kill pill in this hostile downhole environment.
The Galileo Experience
Authors: Koper M. G. M.
Published: December 2007

This paper describes the Underbalanced Coiled Tubing Side tracks executed with a Hybrid Drilling system.

The project was executed from August 1997 to January 1999. During this time a steep learning curve was built on Hybrid drilling Unit technology.

The project comprised three sour gas wells with increasing complexity starting with a through tubing deepening, a world first through tubing double casing exit, through 5" and 7" casing, and finally a short radius side track with a 500 mtr. horizontal section. All three wells are targeted in the Zechstein Carbonate at 3000 mtr. TVD.

The learning curve on the Hybrid Drilling unit and underbalanced surface equipment is described, along with the methods used to manage the risks involved in the introduction of new technology.

The well objectives, drilling for fractures or equivalent matrix production and underbalanced design are discussed.

The different operational stages on the three wells are discussed.
Underbalanced Drilling With Coiled Tubing in Oman
Authors: van Venrooy J , van Beelen N , Hoekstra T , Fleck A , Bell G , Weihe A
Published: December 2007

This paper describes the first few months of operation of a new, purpose built, underbalanced (UB) coiled tubing drilling unit (CTDU).

The unit is designed to drill sidetracks and extensions to existing wells to improve reservoir drainage. The package is fully self-contained, and native crude is used as the primary drilling fluid. Natural gas injection through parasite strings or conventional gas lift mandrels is used to maintain underbalanced conditions.

The paper outlines the drilling and production challenges faced by the operator, including brief overviews of current conventional operations and a trial campaign of wells drilled with coiled tubing. With this background, the expected benefits of underbalanced drilling with coiled tubing (CT) are outlined.

The unit was built during 1998 and mobilised from the USA to Oman at the end of November 1998. Following final construction work and commissioning, the first two wells were drilled during February and March 1999. As part of the commissioning and shake-down process, these wells were drilled overbalanced using a conventional fluids package. The underbalanced drilling process system was integrated into the unit during April 1999 and commissioned in the field prior to initial underbalanced operations on the third well. Details of subsequent operations are included with an overview of drilling performance for the first 5 wells.

The paper concludes that underbalanced drilling technology can be applied safely and successfully. Although the paper deals solely with operations up to the end of June 1999, initial performance indicates that the predicted gains are achievable.
Optimizing Drilling Performance By Wellbore Stability Evaluation And Directional Drilling Practices
Authors: Hassan S. , Klimentos T. , Badri M. , Sengul M. , Zeid A.
Published: December 2007

In this paper we present data from several offshore wells, which have experienced wellbore stability related problems, especially over intervals with higher angles of deviation. We performed a wellbore stability evaluation for several angles of deviation using log, core and drilling data from all the existing wells, in order to predict the optimum drilling parameters to be used in the next wells to be drilled in this area. The answers provided by this study included properties such as, recommended mud-weights (minimum & maximum) as a function of angle of deviation, rock strength, and pore pressure. The determination of the rock strength along with the optimum mud-weight windows improved overall the drilling performance by minimizing washouts, loss of circulation, and optimizing casing design by elimination of unnecessary casing strings. Moreover, improvement of bit performance was achieved by using the predicted rock-strength values. As a result, drilling time and well construction costs were reduced significantly.
A New Hydraulics Model for Slim Hole Drilling Applications
Authors: Hansen Svein A. , Rommetveit Rolv , Sterri Njål , Aas Bjarne , Merlo Antonino
Published: December 2007

A model to predict the pressure loss for slim hole drilling has been constructed. The model, which is constructed by theoretical and numerical analysis and experimental measurements, incorporates the effect of eccentricity, drillstring rotation and rheology.
Integration of Analog Data for Building Testable, Deterministic Geological Models in a Common Interpretation Environment: An Example from the Atokan Boonsville Gas Field, Fort Worth Basin, Texas
Authors: McCormick David S. , Carr David L. , Bryant Ian D.
Published: December 2007

A fundamental problem facing the petroleum industry is to effectively use the large amounts and diverse types of data that are collected to define and exploit stratigraphic and structural compartments that contain undrained hydrocarbons. The key is to build data-driven, deterministic geological interpretations to intelligently target infill wells. This approach is fundamentally different from that used in geostatistically-driven approaches which interpolate the sparse data support points without maximizing the value of the data that has been collected or geological knowledge.

We describe a workstation tool and interpretation method for that allows one to combine, in 3D, well-based interpretation and quantitative analog information from fields or outcrops to make testable predictions about the location of geological bodies that are prospective infill drilling locations. This tool combines (1) 3D visualization in a common viewing environment of diverse data that are viewed at true scale (e.g., 3D surface seismic; vertical seismic profiles, reservoir simulation results, conventional wireline and borehole imaging logs, core photographs); (2) a well-based interpretation environment; and (3) an archive of digital 3D geological analog shapes and textures that one can use to relate textures seen in image logs or core images to those observed in analog data, i.e., other fields or outcrops. These shape and texture analogs can then be used to place geological bodies that can be rescaled and oriented in 3D. Comparison with seismic data may then support or refute these interpretations.

We have applied this tool to the interpretation of the Atokan Bend Conglomerate in the Boonsville Field in north Texas, a mixed siliciclastic-carbonate succession containing deltaic, estuarine, and fluvial valley-fill sandstone reservoirs. The key to exploitation of this field is identifying sandstone bodies within the lowstand, incised valleys, which are commonly less than 500 meters in width, and 20 meters in thickness. By combining core, image log, and seismic information in the 3D visualization tool, we have recognized Bend Conglomerate reservoir sandstone bodies and further, we have been able to define them in inter-well space using sandbody shape analogs from the tool's digital archive.

The key advantages of this approach are that we preserve information about the interpretation process and multiple hypotheses; we see all data at the appropriate scale; and we view the implications of the deterministic geological interpretations within the same data volume as our measured data. This provides a means of capturing and applying geological knowledge of analog formations, as well as tracking the steps in the interpretation process.
High Pressure Crystallization of Deep-Water Completion Brines
Authors: Freeman Michael A. , Slater Kenneth S. , Carminati John R. , Lester G. Scott , Morganthaler Lee N.
Published: December 2007

Deepwater development presents drilling and completion fluids with a new set of conditions: HPLT. This new combination of High Pressure and Low Temperature can induce gas hydrates formation if uninhibited water contacts natural gas. Brine can be a powerful hydrate inhibitor at high concentrations, but solubility (TCT) at mudline temperature limits its use. Recent experience has shown that the brine concentration is limited further because pressure sometimes raises the crystallization point of brine. Testing the brine for solidification at HPLT conditions has required us to develop new instrumentation and through it, a correlation between TCT and PCT at 10,000 psi of deepwater bromide brines.
A Novel Gas-Hydrate Inhibitor for Deepwater Frac-Pack and Subsea Environments
Authors: Nelson Ron D. , Fleyfall Fouad , Dubois Richard , Vitthal Sanjay , Spies Blaine K.
Published: December 2007

A significant number of deepwater fields are being developed with subsea production systems. One of the challenges of using these systems is controlling hydrate formation during initial well startup. Current solutions to this problem are very expensive and operationally challenging. However, a new borate-crosslinked gel system has been developed to prevent hydrate formation under static flowline conditions. This paper discusses the results of experiments performed to validate and compare the new fluid system to conventional borate-gel systems. This inhibited gel system exhibits fracturing-fluid performance equal or superior to that of conventional borate-gel systems. Specifically, the fluid exhibits much lower leakoff than conventional systems. The formation-damage characteristics of this fluid are also superior to those of conventional borate fluids.
Screenless Completions: Cost-Effective Sand Control in the Adriatic Sea
Authors: Pitoni Enzo , Devia Fabrizio , James Simon G. , Heitmann Norbert
Published: December 2007

Many gas reservoirs in the Central Adriatic Sea, offshore Italy, are formed of laminated, low permeability dirty sandstones, with as much as 50% clay content. Initially, wells were completed with gravel packs, but due to the nature of the formations, productivity decreased in some gas fields as fines plugged the gravel packs. In the last few years frac-packs have been used to increase productivity by by-passing near wellbore damage, interconnecting multiple sandstone layers and decreasing fluid velocities in the formation, thus inhibiting fines production.

However, there are many gravel-packed wells which are either sanded up and shut in or underperforming due to fines plugged gravel-pack screens and which cannot currently justify the expense of an immediate full rig workover.

A candidate zone was selected to evaluate the viability of a screenless completion technique for competent sand control to provide a cost-effective and reliable rigless rehabilitation technique. A highly conductive matured tip-screen-out fracture was placed in the zone, using recent innovations in fracturing fluid technology and proppant flowback control additives, to eliminate sand production. Successful implementation of this technique was confirmed by post treatment production more than 2.5 times the normalised rate of the initial gravel-pack completion. No formation sand or proppant were produced back to surface during production.