bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing the Impact of Oil Viscosity Mixing Rules in Cyclic Steam Stimulation of Extra-Heavy Oils
Authors: Mago A. L. , Barrufet M. A. , Nogueira M. C.
Published: December 2007

A global steady increase of energy consumption coupled with the decline of conventional oil resources points to a more aggressive exploitation of heavy oil. Heavy oil is a major source of energy in this century with a worldwide base reserve exceeding 2.5 trillion barrels. Management decisions and production strategies from thermal oil recovery processes are frequently based on reservoir simulation. A proper description of the physical properties, particularly oil viscosity, is essential in performing reliable modeling studies of fluid flow in the reservoir. We simulated cyclic steam injections on the highly viscous Hamaca oil, with a viscosity of over 10,000 cp at ambient temperature, and the production was drastically impacted by up to an order of magnitude when using improper mixing rules to describe the oil viscosity. This paper demonstrates the importance of these mixing rules and alerts reservoir engineers the significance of using different options simulators have built in their platforms to describe the viscosity of heavy oils. Log linear and power mixing rules do not provide enough flexibility to describe the viscosity of extra heavy oil with temperature. A recently implemented mixing rule in a commercial simulator has been studied providing satisfactory results. We also suggest more flexible mixing rules that could easily be implemented in commercial simulators.
Petrophysical Model of Split Shear Waves in Anisotropic Media
Authors: Fanchi J. R.
Published: December 2007

We present a geophysical model of seismic anisotropy that has three velocity solutions: P-wave velocity, and fast and slow shear wave velocities. The geophysical model is used to justify the extension of a petrophysical algorithm in an integrated flow model to a form that is suitable for modeling reservoirs that exhibit seismic anisotropy. The model is illustrated by applying it to data representing limestone and tight sands.
A Model to Predict Liquid Holdup and Pressure Gradient of Near-Horizontal Wet-Gas Pipelines
Authors: Fan Y. , Wang Q. , Zhang H. , Sarica C. , Danielson T. J.
Published: December 2007

A mechanistic two-fluid model with new closure relationships is proposed to predict liquid holdup and pressure gradient of stratified flow. The proposed closure relationships include correlations of wetted wall fraction, liquid-wall friction factor, and interfacial friction factor. An iterative calculation procedure is implemented to solve for liquid holdup and pressure gradient for a given set of operation conditions, pipe geometry, and fluid properties.

Two sets of facilities, a small-scale with 51-mm ID and a large-scale facility with 150-mm ID test sections, were used to tune the model. Superficial gas and liquid velocities were varied from from 5 to 25 m/s, and 0.00025 to 0.03 m/s, respectively in the small-scale facility while they were varied from 7.5 to 21 m/s, and 0.005 to 0.05 m/s, respectively in the large-scale facility. The pipe inclination angle varied from -2° to 2°. The liquid holdup was ranged between 0.003 and 0.12 emphasizing the low-liquid loading two-phase flow.

The tuned model performance was then benchmarked against the high-pressure (up to 90 bar) SINTEF stratified flow data. The model predictions agreed well with measured values of liquid holdup and pressure gradient. The comparison between the present model and OLGA performance was also presented.
Coiled-Tubing Gas Lift Reclaims 2000 BOPD of Lost Crude
Authors: Tischler A. , Woodard T. A. , Becker B. G.
Published: December 2007

The paper describes a successful implementation of coiled-tubing gas lift (CTGL) in the diatomite formation of the Belridge field in Kern County, Calif.

The paper shows how the use of CTGL reclaimed 2000 BOPD that would have been otherwise lost due to irreparable casing damage. As soon as casing damage is detected, the future economic life expectancy of a well decreases to approximately 2 years. Wells with confirmed casing failure must generally be abandoned and redrilled, increasing costs significantly.

The paper will detail candidate well selection, equipment design and specifications. During the program, numerous design challenges had to be overcome. Special wellhead configurations were designed in order to ensure a safe and environmentally friendly operation. Coiled tubing (CT) selection was critical – both to optimize lift volume with minimized injection gas and to insure proper functionality and longevity in a high CO2 corrosive environment. The implementation of the project as well as associated risks and final production results will be mentioned as well.
Collapse Resistance of Tubular Strings Under Geotectonic Load
Authors: Morita N. , Kasahara Y. , Hikida H. , Ito Y.
Published: December 2007

The tubular string collapsing process is significantly different when an external load is applied through a solid formation or a fluid. A series of experiments were conducted to analyze the differences in tubular string stability with a fluid force and geotectonic loads. The laboratory tests showed that tubular strings started yielding significantly earlier if the load was applied through a formation rather than through a confining liquid. However, during additional loading after tubular string yielding, the deformation of the tubular string installed in a formation remained small since most of the external load was supported by the surrounding formation. Analytical solutions were developed to calculate the stress state and deformation before yielding and after yielding for gravel packed or cemented tubular strings under directional in-situ stresses.The API tubular string failure criteria were also modified so that they could be applied to more general stress state around a tubular string.Using the tubular string stress state and the generalized API pipe failure equations, a guideline was given for field design of tubular strings under geotectonic load based on the experimental observations.
Correcting Supercharging in Formation-Pressure Measurements Made While Drilling
Authors: Hammond P. S. , Pop J. J.
Published: December 2007

This paper describes a method to correct formation pressures measured while drilling for the effects of supercharging (increased sandface pressure caused by drilling fluid filtrate leakoff).The method consists of deliberately varying the wellbore pressure, measuring that and the sandface pressure response, and then using a mathematical model, taking account of fluid flows within filtercake and formation to quantify the amount of sandface pressure elevation.The true formation pressure then follows by subtracting this estimate of the supercharging from the actual measurement.The method is explained and demonstrated using synthetic data, and then application to data taken in a real well is shown.
Diluting Acid Gases With Sweet Gases in Gas Lift Systems: Assessment, Challenges, and Recommendations
Authors: Barsoum B. N. , Faramoy S. , Zekry M. M.
Published: December 2007

The offshore oil fields located in the Gulf of Suez (GOS) are sweet oil reservoirs. Edfu field, discovered in November 2001 with total proven reserves between 25 million-30 million barrels, contains sour gas. H2S is extremely toxic; the combination of H2S and CO2 (Acid Gas) can be highly corrosive. Edfu field produces up to 6 MMSCF/day with 800 ppmv H2S and 8 % CO2 in the associated gas phase.

Since 1980&s gas associated with the GOS production is being fully utilized for production of Natural Gas Liquids (NGL) at the fractionation facilities in Gas Plant (GOS G/P U-104) based on some pollution prevention mechanisms. Sales gas is being used as a clean fuel for gas-lifting-oil projects.

During the period of Edfu production it was noted that there is dramatic increase in the acid gases concentration in the gas lift system in addition to recently occurring under-deposit corrosion failure.

This paper describes a case history about de-souring of the Edfu acid gases on the offshore production facilities by diluting (mixing) with other sweet gases produced from GOS area. The work demonstrates the influence of such application on corrosion rates of both gas pipelines and offshore production facilities. Also the feasibility of sweating process considering the incremental recovery of natural gas liquids is included.

This paper shows in a systematic way how to separate H2S and CO2 out at G/P U-104.However, these components must be managed in a cost-effect way and according to regulatory requirements to maximize recovery of hydrocarbons and minimize acid gases safety and environmental impacts.Also we review comparative economic and risk analyses of various H2S management options available to developing low volume of acid gases reserves, considering the impact on G/P U-104 production facilities (including rate, ultimate total volume, engineering capacity), the health and safety risks, impact on environment, and regulatory Issues according to current EGPC standards.
Subsea Smart Multilateral Wells Increase Reserves at Gullfaks South Statfjord
Authors: Haugen V. , Fagerbakke A. -K. , Samsonsen B. , Krogh P. K.
Published: December 2007

The Statfjord Formation in Gullfaks South was discovered in 1978, and came on production in 1999 as part of the Gullfaks Satellite Development.

In the Plan for Development and Operations (PDO) The STOOIP was estimated at 35 million Sm3, with estimated recoverable reserves of 12.6 million Sm3. Start up of the first two wells in 1999 showed that the production rate was lower than expected, most likely as a result of poor reservoir communication. A third well was drilled in 2001 and experienced gas breakthrough shortly after startup. Based on these observations booked reserves were reduced to 2.4 million Sm3 in the reservoir management plan for 2002.

Production has been limited by low connectivity, reservoir heterogeneity and gas breakthrough. Surface operated downhole inflow control and multilateral wells have been identified as solutions to these limitations, which has lead to an increase in expected oil recovery.

This paper describes the process of implementing Downhole Instrumentation and Control System (DIACS) and Multilateral Technology (MLT) in three horizontal subsea wells drilled in 2003 and 2004. This has led to a twofold increase in the reserve estimate to 5.4 million Sm3 in the reservoir management plan for 2005.
Geosteering Using New Directional Electromagnetic Measurements and a 3D Rotary Steerable System on the Veslefrikk Field, North Sea
Authors: Wiig M. , Berg E. , Kjærefjord J. M. , Saltnes M. , Stordal E. A. , Sygnabere T. O. , Laastad H. , Raeper G. , Gustavsson E. , Denichou J. -M. , Darquin A. , Omeragic D.
Published: December 2007

Veslefrikk is a North Sea oil field in its tail-end production period where optimal well placement is critical for the drainage of the remaining reserves. This paper presents two case studies representing different challenges with respect to geosteering. In both cases a newly developed Directional Electromagnetic logging while drilling tool (D-EM) was used together with a fully rotated point-the-bit 3D rotary steerable system (RSS) to achieve proactive geosteering. The LWD tool was able to detect resistivity contrasts in any direction up to 5 m from the wellbore. In the first case the objective was to position a 570 m long horizontal well section 1-3 m below the top of the reservoir sand, thereby attaining maximum distance from the water level and ensuring that no attic oil was left behind. In the second case the challenge was to optimize the amount of oil filled sand along the 1100 m horizontal trajectory, while drilling perpendicular to the depositional direction in a fluvial channel system.

The early detection of the sand to shale boundaries resulted in an increase of 10-15 % in the recoverable reserves for each well compared with conventional geosteering.

The workflow setup for both cases included the use of a Web-based system for communication and data transfer. This ensured efficient decision-making involving geosteering specialists, wellsite geologists, and onshore company personnel.
Modeling Water-Injection Induced Fractures in Reservoir Simulation
Authors: Hustedt B. , Qiu Y. , Zwarts D. , van den Hoek P. J.
Published: December 2007

We couple a fracture growth simulator to a standard reservoir simulator using a two-way communication approach. The new approach allows interaction of two stand-alone software packages in order to capture the impact of both, varying reservoir pressure- and stress fields as well as dynamically growing or shrinking fracture shapes.

At a given time step during the simulation, the pressure field is calculated by the reservoir simulator. We determine the stress field on the reservoir grid. Both, the pressure- and the stress field are needed to evaluate a fracture propagation criterion that is based on a stress intensity formulation. The fracture shape is determined in balance with the fracture fluid pressure and the in-situ reservoir stress field using an iterative procedure.

Currently, the coupled simulator handles fracture growth/shrinkage for horizontally, symmetric fractures with fixed height in a single layer reservoir model. The stress calculations require the reservoir grid blocks to be sufficiently rectangular in shape.

We benchmark the new simulator for a number of different test simulations by comparison. The overall comparison with analytical solutions and/or analytical simulations shows a very good fit.
Assessing the Uncertainty in Reservoir Description and Performance Predictions with the Ensemble Kalman Filter
Authors: Zafari M. , Reynolds A. C.
Published: December 2007

Recently, the ensemble Kalman filter (EnKF) has gained popularity in atmospheric science for the assimilation of data and the assessment of uncertainty in forecasts for complex, large-scale problems. A handful of papers have discussed reservoir characterization applications of the EnKF, which can easily and quickly be coupled with any reservoir simulator. Neither adjoint code nor specific knowledge of simulator numerics is required for implementation of the EnKF. Moreover, data are assimilated (matched) as they become available; a suite of plausible reservoir models (the set of ensembles) is continuously updated to honor data without rematching data assimilated previously. Because of these features, the method is far more efficient for history matching dynamic data than automatic history matching algorithms based on optimization algorithms. Moreover, the suite of ensembles provides a way to evaluate the uncertainty in reservoir description and performance predictions.

Here we establish a firm theoretical relation between randomized maximum likelihood and the ensemble Kalman filter. We also consider examples where the performance of the EnKF does not provide a reliable characterization of uncertainty in the model or performance predictions. Although we have previously generated reservoir characterization examples where the method worked well, here we also provide examples where the performance of EnKF does not provide a reliable characterization of uncertainty.
Advanced Multizone Stimulation Technology
Authors: Lonnes S. B. , Nygaard K. J. , Sorem W. A. , Hall T. J. , Tolman R. C.
Published: December 2007

ExxonMobil has developed two novel reservoir stimulation technologies that enable the rapid delivery of numerous high-quality stimulation treatments within a single cased wellbore. These technologies were developed for the purpose of improving, or enabling, economic hydrocarbon recovery from formations that contain multiple stacked reservoir intervals or require the stimulation of long productive intervals. These technologies:(1) enable the stimulation of multiple target zones via a single deployment of downhole equipment; (2) enable selective placement of each stimulation treatment so that they may be designed specifically for each individual zone to maximize well productivity; (3) provide positive isolation between zones to ensure each zone is treated per design and previously treated zones are not inadvertently damaged; and (4) allow for treatments to be pumped at high flow rates to facilitate efficient and effective stimulation.
Enhancing Collaboration Between Engineering and Operations—A Case Study of Alaska Work Processes
Authors: Anders J. , Cooper K. , Dube A. , Green P.
Published: December 2007

This paper details the collaboration and well information system BP Exploration (Alaska), Inc. has implemented to enhance communication and data sharing between work groups operating the Prudhoe Bay field. Accessing and sharing well information and maintaining quality communication between geographically separate Operations and Engineering teams is an issue in all oilfield operations. Using web-based interfaces and database stores has allowed BP Alaska to efficiently operate on the North Slope.
Simulation of Physical-Chemical Processes During Carbon Dioxide Sequestration in Geological Structures
Authors: Calabrese M. , Masserano F. , Blunt M. J.
Published: December 2007

Underground storage of carbon dioxide, CO2, is one way to reduce atmospheric releases of greenhouse gases. The sequestration of CO2 in a depleted gas reservoir is simulated, incorporating molecular diffusion between CO2 and the natural gas, dispersion, dissolution of CO2 in water, and chemical reactions of the CO2 with the aqueous phase and host rock.

This study is applied to a depleted gas reservoir located in the North of Italy. Since the end of production the field has been used for gas storage, and in this work it has been considered for a pilot project of CO2 injection. The different physical and chemical phenomena acting in the reservoir are simulated to investigate their influence on the total storage capacity. The effect of injection rate, the point of injection and the purity of the injection fluid are analyzed.

While molecular diffusion of CO2 in methane can be neglected, the dissolution of CO2 in water increases the maximum storage capacity. Both the pattern of reservoir heterogeneity and the degree of mechanical dispersion has a notable impact on the results. Particular attention should be given to the composition of the injection fluid, because the presence of impurities strongly affects the total stored mass.

Low injection rates give a larger total stored mass, since gravitational forces act to transport the CO2 to the top of the aquifer, but only after long periods of injection. Near the gas/water contact, the residual gas saturation has a significant impact on storage.Precipitation reactions render the CO2 immobile in a solid phase, but over a very long timescale.
Perforating for Zero Skin: A Study of Productivity Improvement in Ecuador
Authors: Flores J. G.
Published: December 2007

The most significant components in the skin equation that do not depend on nature are invasion damage and perforating-induced damage. The oil industry has approached the invasion issue by using stimulation treatments intended to regain the permeability lost through formation damage, or by deep-penetration perforating aimed at bypassing the invasion damage. Perforating is known to create a low-permeability crushed zone in the formation around the perforating tunnels that also constitutes a flow restriction, which can impair the well's productivity or injectivity. A perforating design that guarantees bypassing the invasion and at the same time eliminates the perforating tunnel damage is crucial in obtaining a zero-skin completion and maximum productivity or injectivity.

This paper introduces an objective methodology to design perforating jobs for zero-skin and maximum productivity. The method is based on theoretical development and experimental studies carried out on cores from three fields in Ecuador's Oriente basin. Simulations using experimental data allowed for modeling the performance of the perforating charges and for determining accurate values for the penetration depth in the actual reservoir rock. The depth of invasion for each of the reservoirs of interest was obtained from modern logs in the case of new wells, or from a statistical study based on pressure transient tests in the case of old completions. By coupling the actual penetration depth of the charges with the radius of invasion, objectively designing perforating jobs to bypass the invasion damage became a reality.

Solving the second part of the problem involved finding a way to produce clean perforating tunnels. Recent research work has shown that fluctuations in wellbore pressure during the first milliseconds after guns fire actually govern the cleanup of the perforating tunnels and not the initial static underbalance, as originally thought. A perforating job that bypasses invasion, combined with a new design that guarantees a dynamic underbalance at all times, has produced outstanding results in over 40 perforating jobs in Ecuador. Historical field data for conventional underbalance perforating in comparable wells show average skin values of +13 vs. -0.5 using the proposed methodology, with typical production level gains of 300 to 400 BOPD.
Benchmarking Deep Drilling Technologies
Authors: Lambert S. W. , Rogers J. D. , Williamson J. R. , Boyer C. M. , Frantz J. H.
Published: December 2007

The U.S. Department of Energy (DOE) has undertaken a baseline study designed to provide current drilling technology and cost bench-marks as reference points in evaluating future cost improvements to be derived from technology advancements.

Deep formations are one of the sources of natural gas that will play an important role in meeting the growing need for natural gas in the U.S. The Energy Information Agency estimated that 7 % of U.S. gas production came from deep formations in 1999. This contribution is expected to increase to 14 % by 2010.

A deep-well database has been completed that categorizes wells by total depth, targeted formation, geographic location, completion technique, and operator. In addition, information was gathered from operators and service companies reporting the current status and future directions of drilling technologies, which was then compiled into a condensed format.

Bit and downhole motor and turbine technology have improved significantly over the past several years, leading to faster rates-of-penetration (ROP) for deep wells. Polycrystalline diamond compact (PDC) bit technology is one of the most significant technology improvements in the drilling industry over the last 20 years.

Current and proposed well-construction methodologies that should continue to reduce costs of drilling deep and extended-reach wells include solid expandable tubulars and the concept of casing drilling or liner drilling. However, these concepts are still evolving.

As these and other new technologies are applied, the results of this benchmarking effort provide the basis upon which future relative progress and cost savings can be identified and measured.
Analysis of LWD Propagation Resistivity Data in Anisotropic, Thinly-Bedded Formations Identifies Significantly More Hydrocarbons
Authors: Boonen P. , Haugland S. M. , Laughlin D. G.
Published: December 2007

Thinly laminated pay zones are often anisotropic. The horizontal resistivity is dominated by relatively conductive shale layers, and the vertical resistivity is dominated by relatively resistive hydrocarbon strata.When the relative inclination is low, conventional induction and Logging-WhilWhile-Drilling (LWD) propagation resistivity tools only sense the horizontal resistivity and triaxial wireline measurements can be used to estimate the vertical resistivity. However, the relative inclination is often high enough to enable accurate determination of the vertical resistivity from the LWD propagation resistivity data and estimates of the structural dips. The vertical resistivity values can then be used to improve identification and quantification of productive intervals. Cases discussed in this paper demonstrate the modeling software for determining these anisotropy parameters, even in thinly bedded sequences. In practice, the results can be determined rapidly enough to affect completion decisions.

A data processing procedure involving anisotropy analysis, thin-bed modeling, and shaly-sand analysis is described in the context of examples wells which penetrate thinly laminated anisotropic beds.After the modeling exercise, it was evident that the vertical resistivity was significantly higher than indicated on any of the raw resistivity curves. Two shaly sand analyses were performed, the first using the raw resistivity curves, and the second using the modeled resistivity values. A comparison of the results from both shaly sand analyses showed that significantly more hydrocarbons were identified after the modeling was done.
Slimhole Drilling with Expandable Sand Screens for Low-Cost, High-Deliverability Wells at Bhit Gas Field in Pakistan
Authors: Mehmood A. , Mazzoni R. , Ahmed J. , Arshad M. , Egge G. , Montagna J.
Published: December 2007

The first ever expandable selective sand screen open hole completion in Pakistan was successfully deployed with combined efforts of the Operator and Service Company operations teams. This installation allowed for recovery of a previously suspended well due to drilling complexities, such as top of the mountain air drilling and shallow H2S issues. Additionally, this installation proved the advantages of slim-hole drilling and the economic benefit of large bores to maximize well productivity by lowering the turbulent skin effect in a high rate gas well. The objective was to design a completion for cost effective 6" slim hole drilling without compromising the targeted well production of 90-MMSCFD achievable from conventional 7" monobore completion.

The project targets were met in terms of both productivity and cost with minor contingencies solved on location. Similar expandable installations will lower the capital expenditure of future high rate gas wells for Eni and its JV partners through utilization of slim-hole drilling while achieving large bore for higher productivity targets.

Sand control in open hole unconsolidated sands with inter bedded clay layers may be considered higher risk completions. This paper will discuss and compare alternative technology solutions available for open hole completions. Additionally, this paper will discuss the operational risks of expandable screen systems as well as constraints of other sand control completions options.

Expandable screen for open hole sand control has become a proven technology providing fast installation, wellbore support, zonal isolation, future water control options, reduction in flow turbulence and mechanical skins, resulting in improved productivities.
Practical Application of Probabilistic Approach to Estimate Reserves Using Production-Decline Data
Authors: Cheng Y. , Wang Y. , McVay D. A. , Lee W. J.
Published: December 2007

Analysts have increasingly used probabilistic approaches to evaluate the uncertainty in reserves estimates based on decline curve analysis. This is because the results represent statistical analysis of historical data that usually possess significant amounts of noise. Probabilistic approaches usually provide a distribution of reserves estimates with three confidence levels (P10, P50 and P90) and a corresponding 80% confidence interval. The question arises: how reliable is this 80% confidence interval? In other words, on a large set of analyses, is the true value of reserves contained within this interval 80% of the time? Our investigation indicates that it is common in practice for true values of reserves to lie outside 80% confidence intervals much more than 20% of the time using traditional statistical analyses. This indicates that uncertainty is being underestimated, often significantly. Thus, the challenge in probabilistic reserves estimation using decline curve analysis is not only how to appropriately characterize probabilistic properties of complex production data sets, but also how to determine and then improve the reliability of the uncertainty quantifications.

This paper presents an improved methodology for probabilistic quantification of reserves estimates using decline curve analysis and practical application of the methodology to actual individual well decline curves. Application of our proposed new method to 100 oil and gas wells demonstrates that it provides much wider 80% confidence intervals, which contain the true values approximately 80% of the time. In addition, the method yields more accurate P50 values. Thus, the new methodology provides more reliable probabilistic reserves estimation, which has important impacts on economic risk analysis and reservoir management.
Models and Methods for Determining Transport Properties of Touching-Vug Carbonates
Authors: Zhang L. , Nair N. , Jennings J. W. , Bryant S. L.
Published: December 2007

In some vuggy carbonate rocks, the sizes of the vugs are much larger than that of the matrix pores and different physical models are required for different parts of the pore space. This is particularly true when the vugs are touching, forming a network of directly connected vugs and creating flow pathways unrestricted by matrix resistance. An additional complication is that vug-to-vug connections introduce another important length scale, the scale of the connected clusters, in addition to the scales associated with the vug sizes and the background matrix variability. Flow and transport properties of these vuggy carbonates often deviate from classical theories and meaningful laboratory measurements are difficult when the vugs are larger than plug samples or whole core. Despite the theoretical and experimental difficulties, estimating effective permeabilities and effective dispersivities in these rocks is of great practical importance in modeling petroleum reservoirs and groundwater aquifers.

In this paper we describe an approach to quantify these properties for a particular class of rocks. The approach combines five techniques: 0.5-mm resolution X-ray CT imaging of a 36 cm high – 25 cm diameter sample, capillary-tube models, bench-scale flow experiments, connected-volume computations, and high-resolution numerical simulation of single-phase flow and solute transport. The approach is illustrated with a sample taken from a Cretaceous caprinid reef debris deposit containing vugs as large as 10 cm. The vugs correspond to void space within and between the irregularly packed caprinid shells and fragments. Connectivity analysis of the CT data shows that more than half of the vug volume is in a single touching-vug network. Even so, the connected path of vugs spanning the sample is restricted and many vugs are the large-scale analogues of "dead-end pores". The consequent variation of effective permeability, 35 md - 114 Darcy, is quantified at the scale of 5 to 35 cm computationally and experimentally. Dispersivity in this sample is a non-trivial convolution of at least three phenomena: advection through a flowing-vug network, transfer between the flowing-vug network and dead-end vugs, and transport through the matrix and non-touching vugs.
Integrated Full-Field Review of Betty Field for Building Predictive Models to Reduce Uncertainty in Reserves and Identifying Future Potential
Authors: Kasap E. , Sanza G. , Kario M. W. , Basu T. , Fathy K. , Claverie M. , Waheed A. , Layh B. , Boitel A. , Gajraj A.
Published: December 2007

A multi-discipline integrated full field review (FFR) was conducted for Betty field, offshore Malaysia, in order to build a set of 3D predictive numerical models from multi-scale geological, seismic, petrophysical, reservoir and production engineering data.This study reassessed field stock tank oil initially in-place (STOIIP) volumes and remaining reserves, determined infill drilling potential and identified opportunities to improve both short-term and long-term field performance.Betty field comprises of multiple stacked, laterally continuous, vertically heterogeneous reservoirs. Some reservoirs have experienced relatively high recovery factor (RF) to date (i.e., >69%), while others have underperformed (RF<15%). One of the priorities of this study was to resolve these anomalies.

Detailed evaluation of the core identified five predominant lithofacies in each reservoir. Horizons, which were interpreted from 3D seismic and tied to the well logs, formed the framework for the static model structure. The neural network-based lithofacies analysis for all the wells enabled distribution of the lithofacies data in a 3D geocellular model, which significantly improved the accuracy of the rock property distribution in the reservoirs. Vertical trend functions based on electrofacies logs were input to control the facies content of each layer, and the resultant facies model was used to control the porosity distribution using Sequential Gaussian Simulation (SGS) throughout a fine grid (11 million cells, 1-ft. layers). SGS was also used as co-simulation for permeability, coupled with vertical and horizontal variograms honoring the appropriate facies proportion in each layer.The static model was upscaled (to 600,000 cells, 6-ft layers) after correlating the lithofacies from well to well with over 2800 geological markers to preserve vertical heterogeneity. The initial saturation distribution determined from gravity-capillary equilibrium and a single J-function anchored at the base of the water-oil transition zone, was essentially corroborated by petrophysical analyses.Representative drainage/imbibition relative permeability curves were established from the available data and deployed for dynamic modeling.

As a testament to the integrity of the data, the technical interpretation and overall approach that was used, it was found that almost 75% of the 66 historical completions were essentially matched for 27 years of history after making trial runs of the dynamic model without any adjustments to the static reservoir description.
Measurement of the Sealing Capacity of Shale Caprocks
Authors: Al-Bazali T. M. , Zhang J. , Chenevert M.xs E. , Sharma M. M.
Published: December 2007

Shales play a major role in petroleum exploration and production because they occur both as source rocks and cap-rocks.Their small pore throat size means that very high capillary pressures are required to establish any hydrocarbon saturation in the shales. The minimum capillary entry pressure (trap capacity) defines the maximum height of a hydrocarbon column that can be trapped by a shale.

In this paper, pressure transmission tests were used to experimentally measure capillary entry pressures of various non-wetting fluids (oil-based mud, crude oil. Decane and Nitrogen gas) through different shales.These capillary entry pressures are needed for the estimation of a shale's seal capacity (h).Results show that measured capillary entry pressure (seal capacity) of shales are correlated with other shale properties such as CEC and permeability.The effects of fluid type and interfacial tension on capillary entry pressure of shales were also investigated.Results show that the presence of a hydrocarbon phase (decane) in the shale reduces the shale capillary entry pressure (seal capacity) and significantly increases hydrocarbon flux. Also, the presence of surfactants in the hydrocarbon phase significantly reduces the capillary entry pressure and, therefore, the shale's seal capacity.Measured capillary entry pressures were also used to estimate the pore throat radius of shales.

Since pressure transmission tests are so difficult to run, a quick and easy rig-site electrochemical test on shale cuttings to characterize the capillary entry pressure of drilled shale formations is suggested.
Pressure Effects on Porosity-Log Responses Using Rock Physics Modeling: Implications on Geophysical and Engineering Models as Reservoir Pressure Decreases
Authors: Holmes M. , Holmes A. M. , Holmes D. I.
Published: December 2007

Due to changes in fluid properties, porosity log responses change with pressure, especially for gas/water systems.Velocity data (compressional and shear) can be described using the Krief rock physics model.This model involves relationships among compressional and shear velocities, rock bulk density, elastic moduli of the matrix, shale and fluid components, shear modulus of the solids, and Biot coefficients.Density response is governed by changing gas density as a function of pressure.Neutron response is controlled by hydrogen indicies of the fluids and the excavation effect.

A complete porosity log suite model is presented whereby pseudo porosity logs are calculated as pressure and gas saturation dependent functions.

Matrix and shale properties are included.Additionally mechanical properties with changing pressure and saturation are available.

From compressional travel time and density log responses, changes in synthetic seismograms as reservoir pressure is reduced can be calculated.This application has significant implications in the interpretation of 4-D seismic surveys over reservoirs undergoing pressure depletion.

Estimates of changing mechanical properties as functions of saturation and pressure have a number of engineering applications, including stimulation design and sand control.

Examples from a variety of clastic and carbonate reservoirs are presented, including intermediate depth hard rocks, deep offshore soft rocks, and shallow onshore soft rocks.
Simultaneous Drilling-Production-Construction Operations: Managing Safety vs. Deliverability on the Peciko Gas Field, Indonesia
Authors: Saintpère S. , Faget J. -B. , Payer N. , Vergnot D. , Baranthol C.
Published: December 2007

The PECIKO gas field is situated offshore East Kalimantan – Indonesia and is a major contributor to the gas production of the region.

Its phased development, scheduled between 1999 and 2008, is based on 7 wellhead production platforms, representing 100 wells (standard and splitter wells). Currently, 58 wells are in production on the 6 different platforms already installed.

Two cantilever Jack-up rigs are permanently assigned to the development of the field and Drilling – Production Simultaneous Operations (SIMOPS) is the common rule.

The Drilling department is Responsible for the Safety and Environment on Site (RSES), inside a 500 m radius zone around the rig, through the drilling supervisor who is officially appointed RSES by the top management of the subsidiary. The RSES is assisted by a "Well Permit Coordinator" offshore and has the full support of the drilling safety & methods teams based onshore.

The first part of this paper will describe the specific measures implemented as standard procedures to reduce the production disturbances while drilling with a jack-up rig on a production platform. In particular, the concurrent drilling, production and well servicing (perforations, clean-up….) activities will be discussed through illustrated examples of both improvements and drawbacks.

The second part of the paper will cover the specific case when a heavy construction program (commissioning of new platforms and their connection to the production network via new export lines) had to be conducted simultaneously with the "usual" SIMOPS described in the first part of the paper. In particular, the different phases will be reviewed: -Coordination between the different entities (operators technical departments, drilling contractors, construction barges contractors….) involved under the leadership of the Drilling department,-Systematic detailed Hazards Identification / Risks Assessment (HIRA),-On-site dissemination of the information and clarification of supervision lines.

The conclusion will insist on the positive financial impact of a well prepared SIMOPS campaign (evaluated in millions of dollars) but also on the HSE aspects thanks to a better evaluated risk (no recordable injury nor major material or environmental incident occurred).
Prevention of Tick Bites on Offshore Wellhead Towers; An Integrated Health, Safety and Environmental Approach
Authors: Newson-Smith M. S.
Published: December 2007

Tick bites represent a significant problem on offshore wellhead towers for the company and its contractors. Over 50 cases per year were reported from one supercomplex alone over a 5 year period.

The health risks to employees are tick bite reactions (including blistering, ecchymosis and gangrene), tick bite paralysis (beginning around 2 days after the bite with weakness in the lower extremities, progressing to falling episodes and incoordination), and tick borne infections (eg Crimean-Congo haemorrhagic fever, the last outbreak in the UAE having a mortality of over 70%).

The ticks were mainly carried by the Socotra cormorant, a migratory bird protected by law.

The approach taken to reduce the incidence of tick bites was to try to reduce the occupancy of the sites by the birds, to reduce the level of faeces containing bird ticks, to reduce worker stay times, and to provide appropriate personal protective equipment.

Bird scaring devices were ineffective and the use of wires would have presented a safety hazard to helicopter operations. Tactile repellents would be ineffective because of the usage of the towers leading to its rapid removal.

Manual cleaning, steam cleaning and grit blasting to clear bird faeces carried increased health risks to the employees carrying out the work which would have had to be frequently repeated given the speed at which the ticks return following cleaning.

The use of insectides would have had an adverse environmental impact and, as with cleaning, would have to be rereated frequently.

Stay times were reduced and instructions given to reduce exposed skin areas by more effective use of overalls. A system of treating overalls using permethrin was developed utilizing onshore laundries given the space limitations of offshore laundry facilities. DEET based insect repellants were also provided. Over a two year period the number of reported cases has reduced by 50%.
Vehicle Data Recorders for Addressing "Driving Behaviors"
Authors: Kazmi S. M. A. , Shaikh A. , Wenspy S. , Rafiq R.
Published: December 2007

Driver behavior contributes to major road incidents, around the world. As behaviors are intangible and very difficult to gauge, for BP Pakistan it was a challenge to introduce right tool for gauging, monitoring and sustaining driver behaviors. This is a case of how behaviors could be molded with fruitful results.
Improve Facility Project Delivery With Methods for Manufacturing Excellence
Authors: Patty R. M. , Denton M. A.
Published: December 2007

Facility project management and control systems can be improved by the infusion of execution planning methods typical of Toyota production preparation. The value of Toyota's just-in-time process is found in its reliability improvement of planning and supply systems, not just that some materials come just as they are needed. Toyota cut the industry standard 3 million man-hour project time (to design and setup a line for a new automobile), by 15 months. Lowered its cost by 1.3 million man hours, and reduced startup time to design production rates and specifications by 62%. Building on last planner1 and lean production2 introduced for construction, by others, the authors present herein, production-level project-execution-planning methods for facilities typical of the oil industry. Early application put a 3000 person project team in the tar sands area of Alberta, Canada on the path to 6 months and 10% savings.
Managing Major Incident Risks
Authors: Smith D. , Zijlker V.
Published: December 2007

Alexander Keilland (1980), Ocean Ranger (1982), Piper Alpha (1988), P36 in Brazil (2001) and a recent major blowout (H2S release) in China (2003) are all well-known examples of incidents that have resulted in major loss of life.

The Safety Management Systems the industry utilises should be equally applicable to the management of all types of risk: from the high frequency, low consequence ‘slips, trips and falls’ to the rare, high consequence incidents. However, the review of past major incidents has shown that the complexity of the failure path is such that questions arise as to how adequate a traditional SMS based approach is to managing these types of incident.

This paper presents some of the major challenges associated with managing major incident risks. It draws upon the findings of a recent workshop organised by the International Association of Oil and Gas Producers (OGP) that specifically addressed key challenges in this area, and identified issues that warrant further review and development.
Target-Time-Based Performance Contract Reduces Well Times and Project Cost
Authors: Lischuk V. Y. , Bakici M. A.
Published: December 2007

Many forms of "beat-the-curve" incentive contracts are in use in the drilling industry to reduce cost and improve project performance. A successful variation involved drilling conventional deviated wells from pads in less than two-thirds of the budgeted time for a lump-sum fee. Modulators, included in the contract to account for nonproductive times (NPT), were subsequently used to adjust the lump-sum fee, depending on the party responsible for the NPT.

Historically, the deviated hole sections were drilled with turbines and local tricone bits requiring multiple trips for bit changes, turbine bent-housing setting changes, and directional surveys. The new plan included the use of a telemetry system, positive displacement motors, and polycrystalline diamond compact (PDC) drill bits. One run per section was targeted, and results were achieved after a few wells by experimenting with several bottomhole assembly (BHA) configurations and PDC design combinations. The wells were drilled in 22 to 26 days instead of the originally planned 40 days.

These results are attributable to a concerted effort by the operator, drilling contractor, and the service companies to identify and eliminate "invisible" NPT by applying fit-for-purpose technology and better planning. Several time-saving practices were also adopted. A main contributor to the success was that the local drilling contractor adopted the mind-set change for all the contractor rigs, including those not associated with the project. Cooperation developed the means to overcome the limitations of the drilling equipment belonging to the drilling contractor: first, an external audit identified critical areas needing immediate improvement, and then these areas were subsequently remedied jointly without creating a heavy financial burden on the drilling contractor.