bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Stress and Pressure on Gas Flow Through Natural Fractures
Authors: Warpinski N. R. , Teufel L. W. , Graf D. C.
Published: December 2007

Gas conductivities of narrow natural fractures in sandstone and chalk were measured under varying stress and pore pressure conditions and showed a decrease in conductivity with increasing net stress. Natural fractures in mudstones exhibited continuously decreasing conductivity upon application of stress, so that correlatable conductivity data could not be obtained. Effective-stress -law behavior for the sandstone and chalk fractures were examined, giving α values in the range of 0.8-1.06, where α is the parameter in the effective-stress law, σ - αP. The value of α for the fracture in chalk was nearly constant, but the values for the fracture in sandstone tended to decrease with increasing stress. Transition Reynold’s numbers and turbulence factors for flow through the chalk and sandstone fractures were determined, yielding turbulence factors ranging from 6.0-20xl06 ft-1 (2.0-6.6x10-5 cm-1) for differently stressed fractures. The entire flow behavior of these natural fractures, including conductivity, effective-stress law, and turbulence, is controlled by stress and pore pressure. As a result, pressure depletion during production will significantly change the productivity of a reservoir with similar natural fractures.
A Type-Curve Solution for Coal Seam Degasification Wells Producing Under Two-Phase Flow Conditions
Authors: Mohaghegh S. , Ertekin T.
Published: December 2007

In this paper a new series of type curves that can be used in the characterization of coalbed reservoirs are presented. The proposed type curves take into consideration the presence of water in the coal seam and its co-production with gas. The developed type curves are capable of handling the presence of the non-linear desorption phenomenon which plays a major role in the flow dynamics of methane in coal seams.

A previously developed numerical model has been instrumental in the construction of the new type curves. During the development phase, gas and water equations were collapsed into a single expression. This consolidated transport expression was then put into a dimension-less form and necessary dimensionless groups were identified. The terms which relate to desorption process were included within the total system compressibility. This was made possible through a newly developed sorption functional group.

The proposed type curves assume radial flow geometry around a degasification well which fully penetrates the formation. These type curves are generated for constant pressure specifications at the inner boundary. Coal seam initially is assumed to be in saturated state. The proposed type curves were tested extensively using a wide range of coal properties including desorption characteristics, and were identified with unique characteristics. The uniqueness of the type curves are preserved throughout the different flow regimes.

The proposed type curve solution for coalbed reservoirs undergoing two-phase flow can be instrumental in analyzing the constant pressure drawdown test data from a degasification well.
Analytical Treatment of Transient Non-Darcy Flow
Authors: Yildiz Turhan
Published: December 2007

Non-Darcy flow is an important factor affecting deliverability of gas and high-rate oil wells. An analytical model describing the transient non-Darcy flow is designed. The model is used to define a better interpretation approach.

The new model has shown that the slope of the straight lines obtained from pressure drawdown and buildup tests are independent of the non-Darcy flow component as long as fluid properties remain constant The increase observed in the slope of semilog straight line for non-Darcy gas flow is due to large variations of gas properties with pressure.

An explicit equation for the rate-dependent skin factor has been derived. Significant differences exist between the explicit equation and the empirical ones cited in the literature.

A method is presented to qualify the size and permeability of mechanical skin region from a multirate test.

The proposed equations are tested using a simulated test.
Pressure Buildup Analysis of Early-Time Data from Coalbed Methane Wells in the Rincon Unit, San Juan Basin, New Mexico
Authors: Vo D. T. , Ohaeri C. U. , Montoya G. L.
Published: December 2007

This study documents a procedure used to analyze pressure buildup data from coal gas methane wells in the San Juan Basin, New Mexico. Because these test data are influenced by both fracture linear flow and wellbore afterflow, our analysis procedure uses rate normalization or deconvolution, fractured well solutions and both single-phase and two-phase pseudo-pressure approaches.

Results obtained from the study demonstrate that this procedure is adequate for complete analysis of the buildup data from coal gas wells. The use of rate normalization and pressure-rate deconvolution can enhance the identification of the radial flow period. Also, because the wells analyzed were hydraulicaily fractured, the fractured well models permit the analysis of early time data. Finally, the two-phase pseudopressure method allows the calculation of absolute formation permeability.

We used this procedure to analyze pressure buildup data from several wells in the Rincon Unit. Results from the analysis are used in reservoir simulation studies of these wells. Simulation model results agree closely with observed well test and field performance.
Testing Green Canyon Wells with a Pressure-Pulse-Controlled DST System
Authors: Healy J. C. , Maratier J. P. , Fruge M. W.
Published: December 2007

Green Canyon development wells are perforated and tested using the IMPULSE* testing method before completion or recompletion. This method allows a controlled underbalance stimulation of unconsolidated formations so that an initial reservoir pressure and reservoir data can be obtained. A pressure pulse controlled drill stem test (DST) system is used to carry out these well testing operations.

This new DST control concept overcomes some of the limitations of conventional DST tools; equipment reliability is increased in difficult well conditions. This new system has improved the efficiency and safety of well testing in this area.
Horizontal Well Pressure Transient Behavior in Stratified Reservoirs
Authors: Suzuki K. , Nanba T.
Published: December 2007

In this paper, investigation of horizontal well pressure transient behavior in stratified reservoirs is presented.

Although many horizontal wells have been drilled and completed in stratified reservoirs consisting of multiple sublayers devided by interbeds of unknown in-situ permeability, the following three aspects concerning the methodology of horizontal well test analysis have never been touched.

The first one is the influence of permeable interbeds. The second one is the heterogeneity among sublayers. The last one is the applicability of the assumption that the drainholes are perfectly horizontal, whereas the real wells often show complicated traces sometimes penetrating one sublayer to another.

In this paper, the aspects mentioned above are investigated using both analytical and numerical methods in order to know when a horizontal well single layer solution is applicable to a stratified reservoir with crossflow. An example of field data interpretation using the insights obtained in the investigation is shown.
Interference Testing of Horizontal Wells
Authors: Malekzadeh D. , Tiab D.
Published: December 2007

Solution to the problem of interference testing of horizontal wells is a major step forward in understanding the fluid flow behavior of horizontal wells and, therefore, to the efficient implementation of the horizontal well technology. These tests provide valuable information about reservoir characteristics such as areal average transmissibility, storage, and degree of communication between wells.

Due to the larger radius of influence and larger contact area of a horizontal well with the formation than its vertical counterpart, this paper suggests that the transmissibility and storage obtained from interference testing of horizontal wells would be much more representative of the formation than the ones obtained from interference testing of vertical wells.

This paper provides the dimensionless pressure and dimensionless pressure derivative type curves for interference testing of horizontal wells and the appropriate equations to be used in conjunction with the type curves in order to determine transmissibility and storage from field data. Solutions were also obtained for interference testing between horizontal and vertical wells. In addition, this paper recommends that the determination of dimensionless pressure at the horizontal wellbore requires calculating the PD function at small values of both YD and ZD
Capillary Oil Entrapment in Crossbedded Sedimentary Structures of Fluvial Sandstone Reservoirs
Authors: Hartkamp-Bakker C. A.
Published: December 2007

Fluvial deposits contain a high percentage of large-scale cross-bedding. The contrasting grain size of adjacent foreset laminae combined with poorly-sorted bottomsets cause a considerable permeability heterogeneity. Permeability measurements of studied outcrop sandstones range from 0.5 to 17 Darcy. Values of reservoir cores from various Dutch gas fields range from 10 mD up to several hundreds of mD. Average permeability values of the poorly-sorted bottomsets are significantly lower than average values of the well-sorted foresets. Adjacent foreset laminae show remarkably sharp contacts in distinctive grain size and sorting. Consequently, capillary characteristics differ per foreset lamina and between foreset laminae and bottomset. Detailed computer simulations show that oil is being trapped in low capillary pressure laminae as soon as surrounding higher capillary pressure laminae and bottomsets are flushed to immovable oil saturation. It is conceivable that considerable amounts of oil, considered movable, could be trapped by capillary forces on a cross-bed set scale.
Two-Phase Flow in Low-Velocity Hilly Terrain Pipelines
Authors: Sarica C. , Shoham O. , Brill J. P.
Published: December 2007

The flow behavior in hilly terrain pipelines with low flow rates of gas and liquid is gravity dominated. For these conditions, steady or unsteady state flow can prevail, even for constant input gas and liquid mass flow rates. The transient behavior of the flow is due to pipeline geometry and the compressible nature of the gas phase. The result is the occurrence of terrain induced slugging which can cause operational problems.

Severe slugging in a pipeline-riser system can be considered as a special case of terrain slugging in hilly terrain pipelines. For this case, the system consists of with a downward inclined section followed by an upward inclined section. Recently, an improved quasi equilibrium model has been developed to simulate the transient flow behavior in pipeline-riser systems.

A new model is developed to simulate low velocity flow in hilly terrain pipelines by extending the improved severe slugging analysis. The model is based on fundamental principles and incorporates the physical phenomena. Flow instabilities can inherently be predicted by the model, and a separate stability analysis is not required.

The new model developed for low velocity flow in hilly terrain pipelines can be utilized to predict the flow behavior under a wide range of flow conditions, including zero net liquid and gas flow, pipeline start up and shut down practices, the effects of pipeline rupture, and variations of inlet flow rates or separator pressure. Simulation of a full scale field pipeline is presented to demonstrate the capabilities of the proposed model. The results show that large amounts of liquid and gas can be produced in a short period of time due to the occurence of terrain slugging, creating a potential operating problem at the outlet of the pipeline.
Large-Scale Experiments Show Proper Hole Conditioning: A Critical Requirement for Successful Cementing Operations
Authors: Beirute R. M. , Sabins F. L. , Ravi K. V.
Published: December 2007

Proper hole conditioning means to establish a hole that is free of cuttings, debris, etc., and that has a mud in a fully "displaceable" or "circulatable" condition to allow the spacer and cement slurries to effectively displace the mud out of the hole.

During this research project, several parameters that influence hole conditioning were investigated using large scale well models. Resistivity probes were used to detect the travel time of "tagged" slugs as they traveled through the models. This allowed measurements of the circulation efficiency or "circulatable hole" (portion of the mud circulating at a given time) to be made during the tests. Resistivity probes were used since currently available "tagging" techniques (liquid calipers normally used in the field) lacked the accuracy that was needed for the research experiments. To simulate hole conditioning across areas of good permeability, for example across pay zones and even partially depleted zones, circulatable hole measurements were made across man-made sandstone cores. Measurements were also made in pipe-in-pipe (impermeable) sections. Different types of mud were used.

This paper discusses the impact of hole conditioning on the outcome of a cementing operation. The paper also includes, based on the data collected, a compilation of practical recommendations for improving hole conditioning and therefore cement job displacement efficiency in actual field application.
Successful Water Control in Openhole Gravel-Packed Completions Within a TEOR Environment
Authors: Peavy M. A.
Published: December 2007

A phenolic resin plugback technique was developed and successfully employed on thirty-two wellbores with open hole gravel packed completions in the Midway-Sunset field during 1987. This program resulted in a sustained water production decrease of 5,850 BWPD and an oil production increase of 256 BOPD. Total revenue and savings from the wellbore plugback project were estimated at $970,790 per year. The project paid out in 120 days. This paper will address the development, implementation, and results of this water control technique. This study demonstrates that control of water production is possible within an open hole gravel packed completion with the use of a phenolic resin. Successful placement of phenolic plugs in temperature environments ranging from 100 F to 200° F were obtained. Influence of this program on wells immediately offsetting the water shut-off wellbores is reviewed.
Thin Polyacrylamide Gels for Water Control in High-Permeability Production Wells
Authors: Zaitoun A. , Rahbari R. , Kohler N.
Published: December 2007

We evaluated a new cross-linking system using nonionic polyacrylamide and an organic cross-linker in the lab for water control applications in high-permeability wells. The thin gel was not very sensitive to salinity and was stable up to 70°C. The reaction was optimal at a pH between 6 and 8.5, and thus under usual reservoir conditions. In this pH range, it was slow enough for the polymer/cross-linker mixture to be injected easily for several hours. After a shut-in time of one day, the thin gel formed in-situ. We compared the thin gel’s performance to that of the single polymer, and ran two-phase flow experiments in high-permeability sandpacks. The thin gel induced a considerable drop in the relative permeability to water (with krw values divided by a factor of 100 and more), while it remained fairly permeable to oil. Selective reduction of krw with respect to kro was an order of magnitude greater with the thin gel than with the single polymer.
Sand Production Prediction Review: Developing an Integrated Approach
Authors: Veeken C. A. M. , Davies D. R. , Kenter C. J. , Kooijman A. P.
Published: December 2007

A reliable, but non-conservative, field validated prediction of sand production is essential to decide whether sand control measures need to be installed during well completion. In this paper, field measurements of sand production are classified and quantified to obtain a better perspective of the downhole situation. Existing sand prediction techniques are presented, critically evaluated and their limitations discussed. The field application of the current generation of sand prediction techniques is described. The importance of integrating field observations, laboratory experiments and theoretical modelling is demonstrated.
Comparative Study of Gravel/Water Packing 12 Gulf Coast Wells
Authors: Thibodeaux G. A. , Gill S. B. , Richard B. M. , Bowman C. W.
Published: December 2007

This paper presents a case history of 13 gravel pack completions in 12 wells which used completion brine (water) as the carrier fluid as opposed to polymer (gel) carrier fluids, such as hydroxyethelcellulose (HEC) and xantham gum (XC). The gravel/water packs were performed in 12 Gulf of Mexico wells during a six month period from mid-1990 to 1991.

The paper (1) describes the evolution of the water packing equipment and procedures used in this case history, (2) presents data in terms of the procedures and the pertinent well data (deviation, zone length, casing size, screen size, completion fluid weight, pump rate, etc.), and (3) post appraises the success of these water packs by examining gravel pack logs and well productivity. The gravel/ water pack procedure described proved 100% successful in providing excellent gravel packs in these wells. Compared to prior gravel/gel packs, the described procedure resulted in superior packs by providing complete (void-free) packing and by eliminating production damage often caused bthe gel carriers.
A Statistical Approach for Predicting Volume of Oil Spill During Pipeline Operations
Authors: Kim B. I. , Sharma M. P. , Harris H. G.
Published: December 2007

This paper presents statistical models for predicting volume of oil spills in pipeline failures. It is based on performance and failure data of cross-country oil pipelines.

The two-parameter Welbull distribution was used to predict the size (volume) of the oil spill. The goodness-of-fit for the models has been evaluated using Chi-square criterion. The two-parameter Welbull distribution proved to be an effective means of statistically predicting oil spill size.

The statistical models developed make it possible to assess both the probability of volume of oil spillage due to all causes of pipeline failures, and of individual causes as well.
Recompletions Using Large-Diameter Coiled Tubing: Prudhoe Bay Case History and Discussion
Authors: Blount C. G. , Ward S. L. , Weiss T. D. , Hightower C. M.
Published: December 2007

The paper describes the recompletion of an oil well in the Prudhoe Bay field using coiled tubing (CT) in the first use of two inch outside diameter (OD) CT. The CT and currently available auxiliary equipment were installed inside of the existing production tubing to improve flowing tubing hydraulics. The feasibility of relatively large CT for production tubing is demonstrated. In the example well, installation of coiled tubing enabled a "dead" well to be restored to production at a rate of several hundred barrels per day without an expensive rig workover or modifications to existing wellhead or downhole equipment.
The Development and Use of a Coiled-Tubing Simulation for Horizontal Applications
Authors: Misselbrook J. , Wilde G. , Falk K.
Published: December 2007

Thorough analysis of the many circulation parame- ters and force conditions experienced with coiled tubing has helped to improve job efficiency and eliminated many of the operating difficulties experienced in the past.

The arrival of horizontal well technology has pro- duced the need for more diversity and greater reliability from coiled tubing. Many standard completion and work-over operations now require the use of coiled tubing in order to gain access to the horizontal sections. Using recognized correlations for all of the circulation parame- ters involved, and incorporating them into a set of force balance equations, a completely interactive model has been constructed to analyze flow conditions and tubing force effects and predict the outcome of coiled tubing operations.

This paper will describe some of the concepts used to develop a coiled tubing simulator, its operating fea- tures and a few horizontal well examples to demonstrate its capability.
Renovate Produced-Water-Treating Facilities To Handle Increased Water Cuts
Authors: Murti D. G. K. , Al-Nuaimi H. R.
Published: December 2007

The modified skimmer tanks have consistently demonstrated superior oil recovery characteristics compared to conventional design in an oil field tank battery system. The modified tanks have been in continuous service for more than 2 years in one of the oldest oil fields in the Arabian Gulf. The new design has helped recover skimmed oil from a mere 6 bpd (1.0 m3) to more than 55 bpd (8.75 m3) from produced water in a tank battery system alone. The recovery is expected to improve by upto 2U0 bpd (31.8 m3) once skimmer tanks in all the tank batteries are upgraded to the new design.
Identification and Properties of Modified Zeolites for the Removal of Benzene, Toluene, and Xylene From Aqueous Solutions
Authors: Janks J. S. , Cadena F.
Published: December 2007

"Tailored" zeolites, made by exchanging amines onto natural zeolites, were studied as an adsorption medium for the removal of BTEX from saline produced water. The major components in natural zeolites are smectite, clinoptilolite and cristobalite. BTEX levels were reduced a minimum of 70 to 85% in the produced water after treatment. X-ray diffraction was used to analyze the natural and tailored zeolites.
Assessing the Effects of Microbial Metabolism and Metabolites on Reservoir Pore Structure
Authors: Udegbunam E. O. , Adkins J. P. , Knapp R. M. , Mclnerney M. J. , Tanner R. S.
Published: December 2007

The effect of microbial treatment on pore structure of sandstone and carbonatereservoirs was determined. Understanding how different bacterial strains and their metabolic bioproducts affect reservoir pore structure will permit the prudent application of microorganisms for enhanced oil recovery. The microbial strains tested included Clostridium acetobutylicum. a polymer-producing Bacillus strain, and an unidentified halophilic anaerobe that mainly produced acids and gases. Electrical conductivity, absolute permeability, porosity and centrifuge capillary pressure were used to examine rock pore structures. Modifications of the pore structure observed in the laboratory cores included pore enlargement due to acid dissolution of carbonates and pore throat reduction due to biomass plugging. This paper shows that careful selection of microbes based on proper understanding of the reservoir petrophysical characteristics is necessary for applications of microbially enhanced oil recovery. These methods and results can be useful to field operators and laboratory researchers involved in design and screening of reservoirs for MEOR. The methods are also applicable in evaluation of formation damage caused by drilling, injection or completion fluids or stimulation caused by acids.
Study of Effects Upon Gravel-Pack Systems During Frac-Pack Operations
Authors: Donovan J. F. , Johnson M. H. , Salerni J. V.
Published: December 2007

The paper will present effects upon the downhole gravel pack system as "FRAC-PACK" operations are occurring. The testing conducted forthis paper will observe and report upon key elements of the downhole system and fluids. These key elements include but are not limited to the slurry, sand, downhole gravel pack system, casing and perforations.
Analytical and Experimental Evaluation of Expanded Metal Packers for Well Completion Service
Authors: Dreesen D. S.
Published: December 2007

Tandem expanded metal packers are proposed as an alternative to open hole packers and cemented liners for zone isolation in hostile well environments. Packers made of ductile steel tubes can be inflated and plastically enlarged to conform, attach, and seal to the wellbore. Metal packers promise a method to achieve permanent zone isolation in wells where cemented completion liners or traditional open hole packers do not provide satisfactory or economic completions.
Nuclear Magnetic Resonance Relaxation in Porous Media
Authors: Jerosch-Herold Michael , Thomann Hans , Thompson A. H.
Published: December 2007

With the recent introduction of the new generation Magnetic Resonance Imaging Logging (MRIL) tool, it is now possible to make down hole measurements of the proton spin-spin relaxation times, T2, and the spin-lattice relaxation times, T1. It has been previously demonstrated in laboratory measurements that the surface-to-volume ratio and fluid permeability can be estimated from T1 measurements. Permeability values derived from T1 measurements are sensitive to the magnetic impurities and magnetic heterogeneities that determine the surface relaxation velocities. The analysis of T1 measurements is usually complicated by the combination of random internal magnetic field gradients and fluid diffusion. Alternatively, diffusion effects can be quantified using the CPMG pulse train spin-echo experiment with variable pulse spacings. The internal gradients are determined by the pore space geometry and therefore the transverse relaxation of the fluid spins in the presence of these gradients can lead to an estimate of characteristic length scales of the pore space and of the fluid flow permeability. Our experimental results indicate that this permeability estimate is less sensitive to the surface relaxation velocity than are permeability estimates based on T\ measurements. Permeability estimates based on the results CPMG T1 experiments on several sandstone cores are presented.
Computation of Heat Transfer in Wellbores With Single and Dual Completions
Authors: Barua S.
Published: December 2007

Algorithms are presented which permit detailed heat transfer (conduction, convection, and radiation) calculations in wellbores with single and dual completions. The dual completion configuration may consist of parallel or concentric strings. Production or injection modes can be simulated. The annular spaces can be solid, liquid, or gaseous.

The algorithms are incorporated in a steady-state multiphase flow simulator for pipelines, networks, and production systems1. Temperature and pressure profiles in the flow strings are generated by coupling the momentum and energy balances in the strings with the transient heat transfer to the surrounding formation.

Several example problems are analyzed with the algorithms. These include flow and structural configurations commonly encountered in dual completion wellbores. The predicted pressure and temperature profiles are consistent with physical phenomena.
How To Design for Annulus Fluid Heat-Up
Authors: Adams A.
Published: December 2007

Existing single-string analysis methods are inadequate for solution of heat-up problems, which require a global analysis of the whole well system (all casings together). This paper presents a method for such a technique, termed global service life analysis, and describes an FE program (ADHOC) developed to implement it. The formulation is fully general, and is applicable to a wide range of casing design problems.
Subsidence Monitoring in the Gulf Coast
Authors: Green D. E.
Published: December 2007

In certain geological environments, hydrocarbon and mineral production can cause collapsing or subsidence of the local geostructure. Significant subsidence causes casing failure, either in the producing zone or in the overburden. Subsidence can be transmitted through the overburden to the surface causing major problems such as rig collapse or pipeline failure. Early detection of a subsidence problem is important so that measures can be taken to prevent the loss of the well or a potential blowout situation.

At the request of several operators, a technique has been developed for detecting small shifts in the formation or casing which indicate the onset of a subsidence problem. A pilot program using existing wireline tools (Fig. 1) was started in November 1990 on a well in the Gulf of Mexico. The technique and results of this project are presented in this paper.

This technique uses existing downhole wireline tools configured to provide high-resolution measurements. Core bullets (with no retaining wires), tagged with a very low-level, short half-life radioactive isotope (5 microC of cobalt 60,5.2-year half-life), are shot into the formation at regular intervals. After casing is set, a base log is run to determine the precise location of the casing collars and radioactive markers prior to production. Once production has begun monitor logs are run at regular time intervals to detect movement of the collars or markers. Any shift in the locations of the collars or gamma ray pips indicates casing deformation or formation subsidence. The analysis technique relies on detector spacing, rather than cable motion. Subsidence results are presented in graphical form as well as tabular listings.
Performance of a Thermal Horizontal Well Pilot
Authors: Adegbesan K. O. , Leauté R. P. , Courtnage D. E.
Published: December 2007

Production performance of Esso Resources Canada Limited’s Horizontal Well Pilot I (HWPI), recovering10 degree API bitumen from Cold Lake, is described. The well has utilized a vertical steam injection well since 1980. Over 50,000 m3 of bitumen have been recovered at a cumulative oil-steam ratio (OSR) of over 0.35 during the first eight years of operation.

A comprehensive field monitoring program of HWPI was undertaken including well bottomhole pressures and temperatures, reservoir temperatures, interwell radioactive tracer tests, surface seismic surveys and cased hole logs. Approximately 20 to 30 percent of the original bitumen in place in a thermally drained zone, inferred from measured surface seismic data, was recovered. A wellbore utilization of approximately 98 meters or 40 percent of the total horizontal slotted liner length was estimated based on the surface seismic anomalies and bitumen production data. This finding was confirmed from the results of a successful numerical simulation history match of this pilot.

Analytical models have identified that pressure drive mechanisms dominated the early life of the well, with gravity drainage accounting for most of the production later in the well’s life.
Reservoir Engineering of a Geologically Complex North Sea Eocene/Palaeocene Reservoir With Highly Unfavourable Mobility Ratio and Gas/Water Coning
Authors: Moralee T. A. , McDonald B. J. , Phillips D. R.
Published: December 2007

The Gryphon field is a North Sea Eocene/Palaeocene reservoir at the forefront of a new generation of complex oilfields requiring innovative analysis methods for successful evaluation and development planning. In order to correctly simulate reservoir and production complexity in an efficient and rapid manner, novel reservoir characterisation techniques and methodologies of building a full-field model have been utilised and are described below. To alleviate both gas and water coning problems and optimise recoveries, it is planned that horizontal wells will be an integral part of field development.
The Milk River Shallow Gas Pool: Role of the Updip Water Trap and Connate Water in Gas Production From the Pool
Authors: Berkenpas P. G.
Published: December 2007

It has long been known that the Milk River A Gas Pool is located downdip of an aquifer which outcrops in Southern Alberta. In the past numerous suggestions have been made explaining how this unconventional trap of gas below water could exist. These suggestions were without theoretical or practical application. In this paper a theoretical model of the trapping mechanism is described and provides a clear explaination of the phenomenon. It is shown that buoyancy forces are not dominant until pore throats become larger and interfacial tension forces are less than buoyancy. A pressure-depth plot for the Milk River provides additional understanding of the hydrodynamic state of the water and gas in the pool. Application of the theoretical model also provides a basis for understanding edge wells whose production and recoveries are influenced by the aquifer.
Predicting Recovery of Gas Reservoirs Under Waterdrive Conditions
Authors: Hower T. L. , Jones R. E.
Published: December 2007

An analytical model is presented which predicts the performance of gas reservoirs producing under water-drive conditions. The model incorporates a modified water influx technique which accounts for pressure gradients and relative permeability effects across the water invaded region of the reservoir. Under certain conditions in gas reservoirs, these effects can cause significant deviations in predicted performance from that behavior projected using conventional water influx theory. The conditions necessary for this to occur and the improvements realized by using the modified approach are discussed in detail. In addition, the results of the analytical model are compared to solutions generated using a radial, numerical simulator.

Previous work has shown that for water-drive gas reservoirs, ultimate recovery increases with decreasing permeability, trapped gas saturation and aquifer size, and increasing fluid withdrawal rates. However, these parameters are all interrelated. Gas recovery cannot be determined based on one factor without considering the influence of the others. Thus, this paper details the development of new parameters which incorporate the key factors that influence gas recovery. These parameters describe the shape of the p/z performance curves for the reservoir and allow the engineer to estimate the ultimate gas recovery for a particular reservoir/aquifer configuration.
Oilfield Development and Protection of Natural Resources within the Tropical Marine Environment of the Rowley Shelf, Northwest Australia
Authors: LeProvost M. I. , Gordon D. M.
Published: December 2007

In recent years a number of oilfields have been developed in tropical waters of the Rowley Shelf, north-west Australia. Along with Bass Strait and the Timor Sea, this region is the focus for Australia's current oil exploration and production. It supports major coral and mangrove habitats and fishing grounds sensitive to the effects of oil pollution.

Much of the information on the nature and extent of the marine habitats has been gained through survey and monitoring undertaken by oil companies as part of specific development applications in the region.

This paper provides a synthesis of the Rowley Shelf marine environment and reviews procedures protecting the marine resources of the region from the effects of oil spills. Recent government and industry initiatives for improving the protection of the environment are outlined and discussed on the basis of the improved understanding of the marine resources and experience being gained in oil spill contingency planning. The tropical habitats of the Rowley Shelf occur within the Indo-Pacific Zoogeographic Region, therefore experience gained in Western Australia is applicable to similar environments in the South East Asian region.
Pressure-Transient Testing at Drilling Stage of Well Development
Authors: Miska S. , Luo Fang , Lee R.
Published: December 2007

While the DST, RFT and production tests provide useful information for predicting reservoir inflow performance, they require specialized equipment and result in a considerable increase in the cost of operations. Also, conventional, single well pressure transient tests do not provide information on vertical and horizontal permeability. The characteristic feature of the proposed technique is that the test can be conducted by making use of drilling facilities. The tests can be performed at various degrees of wellbore penetration into a formation, hence, the vertical and horizontal permeability can be determined based upon testing of just a single well. The test consists of two major steps. First, a desired drawdown is induced by pumping down the drillpipe and up the annulus a fluid with a density less than the drilling fluid. Upon obtaining a certain amount of oil, the well is shut-in for a pressure buildup. To demonstrate the feasibility of the proposed technique and to reveal the major merits and disadvantages, a computer program has been developed. The simulator enables prediction of flowing and shut-in bottomhole pressures and flow rates under the test conditions if the reservoir and wellbore data are known. Also, the paper consists of the description of the inverse problem. Namely, determination of the reservoir pressure and permeability if the flowing or shut-in bottomhole pressure is given.
Review of Research Efforts in Coalbed Methane Recovery
Authors: Metcalfe R. S. , Yee D. , Seidle J. P. , Puri R.
Published: December 2007

The production of coalbed methane in the United States dates back to the early 1930's. Yet it was not until the early 1980's that research and development projects began to show the enormous potential of this energy resource. These efforts have resulted in the rapid commercialization of coalbed methane production in the United States, including the drilling of almost 800 wells by Amoco. Efforts to evaluate and implement coalbed methane recovery projects are continuing, with current emphasis being placed on worldwide resources.

In recent months, we (and our colleagues) have published almost a dozen papers on coalbed methane production encompassing a wide variety of topics. This paper summarizes the significant findings of those papers and stresses their importance to field operations. Subjects covered include reservoir modeling, pressure transient analysis, rock property measurements, well stimulation, and enhanced coalbed methane recovery. Although most of the work discussed here was done on coals from the San Juan (Colorado and New Mexico) and Warrior (Alabama) Basins, the results are general and applicable to coals in other parts of the world.
A Systematic Approach to Well Design
Authors: Heijnen W. H. P. M.
Published: December 2007

One of our core activities is the design and deployment of exploration and production wells. Since the technology in this area is advancing and therewith the variety of possible well designs it is of paramount importance to re-assess our well design methodology. This paper explains, in concept, the system components and their relationship in performing a well design in a systematic manner. This will provide optimisation of the design as well as providing an audit trail for future performance assessment of the well design. The business aspect and the management of the execution phase will be briefly touched upon in relation with the well design as a basis for technical terms and conditions of a contract as well as Quality Control during the execution phase.
Environmental Protection: Balancing the Risks
Authors: Miller D. N.
Published: December 2007

The pressures on all businesses to manage their environmental performance responsibly continue to grow. Whilst the pursuit of environmental excellence is frequently costly (in financial and resource terms), it is nevertheless fundamental to the continued success of many companies. This is particularly true for companies operating in the primary sector - heightened public and political concern about the environment is reflected in an ever-increasing regulatory burden and in more stringent enforcement of legislation.

Activities such as the development of offshore oil and gas reserves will inevitably have an impact on the environment. This paper will examine the areas of potential environmental risk which these activities pose and review the pressures and potential liabilities for those operating in the sector. It will include an update on the Commission's proposed directive on civil liability for environmental damage caused by waste. It will then consider how risks can be minimised whilst still maintaining efficient and profitable operations.

Examples of best practice, new technology developments and changes in management procedures will be used to illustrate how environmental risks can be minimised.
Hardware and Software Techniques for Pipeline Integrity and Leak Detection Monitoring
Authors: Turner N. C.
Published: December 2007

This paper reviews techniques for leak detection monitoring on subsea pipelines. Five established leak detection techniques and one emerging technique are reviewed. In each case the area of applicability of the technique is considered.

The capacity of each technique to identify the location of the leak is also considered.
The Use of Dynamically Positioned Units in Subsea Completions Offshore Brazil
Authors: Moreira J. R. F.
Published: December 2007

The intent of this paper is to document the major accomplishments achieved in the completion/workover of 28 wells using dynamically positioned (DP) units in the Campos Basin. The initial jobs were performed on wells equipped with conventional guideline trees and drilling bases and located in areas congested with subsea facilities.

Minor changes of equipment design and operational procedures, permitted the successful performance of DP units on those conventional equipment.

Based on the experience acquired from the forementioned jobs, guidelineless trees were designed and successfully installed in the Marlim field, at water depth beyond 700 m.
Rig Computer System Improves Safety for Deep HP/HT Wells by Kick Detection and Well Control Monitoring
Authors: Weishaupt M. A. , Omsberg N. P. , Jardine S. l. , Patterson D. A.
Published: December 2007

A drilling contractor has installed and operated on several offshore rigs, a comprehensive data acquisition and computer processing system for realtime monitoring of drilling operations and post event analysis. The system, which includes "smart alarms" for early warning of problems such as kicks, stuck pipe and drillstring washouts, has been extended to cover recent recommendations of the UK Department of Energy for High Pressure/High Temperature (HP/HT) wells.

In this paper we describe the extensions to the system, developed with a major operator, which continuously monitor the return line valve status, mud pumps, choke manifold and BOP stack to ensure that all components are operating within their design limits.

Although the smart alarms for early kick detection reduce the size of an influx, the problem of circulating out a kick remains a hazardous procedure requiring close monitoring. The system's existing realtime displays of log and digital data include a dedicated screen for well control to provide the necessary monitoring.

Additional HP/HT monitors, which continuously display choke position, BOP terrperatures and separator pressures as required for the North Sea, have been added. Hard copies for detailed analysis are produced from a workstation linked to the network.

The development and operation of this system are discussed, and the benefits in terms of improved safety and environmental protection are demonstrated.
Jack-Up Drilling System (J.U.D.S.)
Authors: Cromar S. A. , Schwelm E. R.
Published: December 2007

This paper describes the design and prototype testing of a 15,000 psi, next-generation surface wellhead for jack-up drilling. The system features metal-to-metal annulus seals and an adjustable mandrel hanger which allows space out and permits controlled pre-tensioning of casing strings above conventional mudline suspension systems.
Minimizing Risks in High-Temperature/High-Pressure Cementing: The Quality Assurance/Quality Control Approach
Authors: Vidick B. , Acock A.
Published: December 2007

High-temperature cementing (above 300°F(149°C) remains a complex operation from job design and execution viewpoints. Temperature prediction is of crucial importance and is still a challenge. To design a slurry with excellent properties (thickening time, rheology, stability and fluid-loss) remains difficult in deep hot reservoirs. The execution of the job is also another critical step: accuracy in additive concentration and constant density are not always easy to achieve using normal cement mixing equipment. All these issues make the cementing of a high-temperature/high-pressure well a critical operation. A new global approach is proposed to minimize the risk associated with these operations. Emphasis is placed on quality control of the materials to be used as well as a quality assurance program for the laboratory testing to give confidence in the results obtained. Quality control of the job execution is also heavily emphasized.
Evaluation of Scale Inhibitors for Downhole Squeeze Treatment
Authors: Braley N. J. , Brunt D. C. , Payne G. E. , Wolf N. O.
Published: December 2007

Chemical squeeze treatment with scale inhibitor has been used extensively to combat downhole scale problems in the Murchison and Hutton fields in the North Sea. Considerable success has been achieved for several years. As the fields mature increasing amounts of water are being produced. These increasing volumes of water require ever larger volumes of chemical for control of scale. A review of the chemicals presently available for squeezing was carried out, with a view to obtaining more efficient squeezes, which would in turn reduce costs of scale control. The risk of an unsuitable chemical plugging a well justified considerable effort being expended in the evaluation.

This paper describes the background to the evaluation process which included two new approaches. The ability to monitor accurately chemical returns in the produced fluids is paramount to a successful and efficient squeeze programme. The accuracy of detection methods was evaluated prior to looking at the effectiveness of the inhibitors. The likelihood of formation impairment during the squeeze process was assessed from core studies. Squeeze life ultimately determines squeeze efficiency and simulation of mini-squeezes on cores was used to gauge minimum squeeze life as part of the commercial evaluation.
Drillstem Test and Closed-Chamber Drillstem Test Simulation
Authors: Petak K. R. , Finley D. B. , Coble L. E.
Published: December 2007

The Drillstem Test (DST) has been a popular form of well testing since the early 1900's. To aid in the completion process, the pressure response from a DST can be analyzed to determine formation pressure, permeability, and amount of well damage. A downhole valve is used to control flow into the wellstring in most DSTs. Typically, the reservoir is intermittently flowed and shut-in multiple times. A variation of a DST is a closed chamber DST.

Usually, the DST buildup periods are analyzed by using Homer3 time or Odeh and Selig's5 method. Limited analysis capabilities exist for the flow periods. Most DST analysis techniques lack the completeness to obtain accurate reservoir parameters.

This paper presents a numeric simulator which is used to model DST and closed chamber DST behavior for a wide range of reservoir and wellbore conditions. Because variable wellbore conditions are considered, analysis is more reliable and often possible when other techniques fail.

Reservoir flow into the wellstring is controlled by wellbore and reservoir parameters. In this simulator, wellbore conditions are modelled by using a wellstorage coefficient which is solved at each time step by performing a mass balance on the wellstring fluids. Volume of produced reservoir fluid, rathole mud production, variable cushion pressure, closed chamber air compression, inner wellstring diameter changes, hole deviation, and variable wellstring volume are considered in the calculation. By accounting for these parameters, this model is more complete than existing models or analysis techniques. The wellstorage coefficient is linked with reservoir values to solve for rate and pressure.

Simulated pressure profiles are presented for various reservoir and wellbore conditions. A simulated match of field test data is also given to illustrate the practicality of this work. The strengths and weaknesses of the simulator are briefly cited.