bluuebunny/crossref_metadata_2025 huggingface dataset:
Reservoir Performance Analysis of Arab "D" Zone (Bahrain Field)
Authors: Murty Challa R.K. , Fathalla Mohammed , Al-Mahroos Faisal M.
Published: December 2007

This paper reviews the case history of a saturated oil reservoir for the past ten years and examines the EOR prospects. The reservoir is overlain by a thick gas cap and underlain by an active aquifer and thus producing by a combination of gas cap expansion and water drive with slight contribution by solution gas. Material balance calculations indicated that the water drive is becoming more active. However, the study suggested that the oil band has not migrated into the gas cap as yet. This is possibly due to the presence of less permeable shaly lime stringers in the reservoir. If the pressure decline continued causing enough pressure differential for these stringers to break down, the oil band may move into the gas cap and some of it may be lost as irreducible oil saturation.

To offset this, gas injection followed by recycling is found the most suitable method to recover the reserves efficiently. This process may find application in reservoirs of a similar nature wherever a sufficient gas source exists.
Increased Fracture Penetration and Productivity using Xanthan Gelled Acid in Massive Carbonate Formations
Authors: Molon J. -P. , Fox K. B.
Published: December 2007

A measurable improvement in productivity can be achieved using xanthan gelled acid to stimulate carbonate formations. Well productivity results were compared to conventional acid fracture treatments. The significant improvements over classical acid fracturing techniques are due to the improved control of acid leakoff rates, retarded reaction rate and improved fracture width maintenance.

The difficulties involved in acid fracturing massive Middle East carbonate formations are discussed and solutions are proposed using gelled acid technology. Some limitations in computer predictions of acid fracturing results are also discussed.
Effect of Polymer Adsorption on Mobility Ratio
Authors: Omar A. E.
Published: December 2007

Several properties of two of the viscous polymer fluids used in reheological control were investigated. Polymer adsorption on the rock surfaces of porous sandstones and its effect on permeability of producing formation was studied.

A naturally occurring polymer, a Guar gum, was found greatly to reduce the permeability of the producing formation, although the use of a breaker solution was found to restore the permeability lost through polymer plugging. Use of appropriate breaker solution was found to reduce the loss permeability to only one or two per cent of the original value.

Adsorption of the synthetic polymer, acrylamide, was found to be directly related to the shaliness of the porous sand. Deactivation of polymer due to adsorption was found to be significant in formations having large surface areas. The results indicate that polymer loss eventually results in a water bank ahead of the polymer solution and thus greatly reduces the polymer's effectiveness in water-flooding.
Design of a Pilot Polymer Flood in the Marmul Field, Oman
Authors: Teeuw D. , Rond D. , Martin J. H.
Published: December 2007

The Marmul heavy-oil field is located in South Oman in the province of Dhofar. The main sandstone reservoir consists of glacial deposits of Permo-Carboniferous age and contains about 2.5 billion barrels STOIIP of 21° API crude. The field is in the stage of primary development with a current production of 45000 BPD.

Oil production by depletion is expected to be low, while a water drive will be adversely affected by the high oil viscosity and high permeability. Thus the Marmul field offers ample scope for EOR techniques, for which two methods have been selected, viz. steam injection and polymer injection. In view of the long lead times involved early testing of these techniques is planned.

This paper deals with the design of the relevant polymer flood and pilot tests. A suitable mobility ratio is determined from calculated drive efficiencies and related polymer requirements, allowing for polymer retention and for viscosity grading of the polymer flood. In the selection of a candidate polymer, attention is paid to viscosifying power, retention characteristics, plugging tendency, shear stability, and last but not least maximum operational flexibility in the field. As for the latter, a liquid polymer seems preferable to a powder polymer.

Results of laboratory experiments indicate that polyacrylamide emulsion polymers provide attractive properties for application in Marmul. Retention in the highly permeable sands is low and so is the plugging tendency. However, viscoelastic effects cause very high pressure gradients at high flow rates, which may adversely affect polymer injectivity. This can be resolved by subjecting the solution to controlled shear treatment prior to injection.

Numerical simulations predict that the oil recovery is substantially enhanced by polymer injection. To have a qualitative Indication of the sweep efficiency improvement in the first (inverted five-spot) pilot test, it is proposed to have the polymer drive preceded by injection of a limited volume of water. The reversal in oil cut should then provide an indication of the better sweep.
New Techniques To Measure and Control Corrosion and Thermal Stability of Drilling Fluids in Deep Wells
Authors: Moussa M. M.
Published: December 2007

Problems associated with geothermals and deep well drilling can be minimized by the proper choice and control of the drilling fluid formulation. High temperature gelation tendency of conventional muds has been avoided by employing the sepiolite (sea mud) systems. Several formulations are tested at elevated temperatures ranging from room temperature to 500°F. Also, the pH value, flow rate and pressure were changed to examine their effect on mud stability. The drilling operation is simulated in the laboratory by two flow loops.

The corrosion rate is measured under the above conditions by the weight loss technique. Three different corrosion cells were used in this study; each one is designed to suit a specific technique. Each cell is loaded with two flat coupons of mild steel (1018). The weight loss of the specimen before and after the run during a certain period of time is a measure of the corrosion rate. The corrosion rate is minimized by adjusting the pH value and the formulation of the fluid. Corrosion rates are measured using different techniques—the flow loop, rolling and static. A new mag-corrosion cell has been incorporated in the loop to combine the rotational motion and the linear flow of the fluids in the annulus. Different mud formulations have been tested.

Correlation between techniques under different conditions are included. The coupons in the flow loop experience change in temperature from room temperature to the test temperature in one cycle with about 15 cycles per hour in one run.

Corrosion is higher when using the mag-corrosion cell than when using the linear flow when both are exposed under the same conditions. Static technique rates are less than rolling. Critical pH values are determined for specific drilling fluids.
Minimizing Casing Corrosion in Kuwait Oil Fields
Authors: Agiza M. N. , Awar S. A.
Published: December 2007

Corrosion in production strings is a well known problem in Kuwait oil fields. Failure to remedy the affected wells results mainly in (1) undesirable dump flooding of the oil reservoirs, (2) or oil seepage and hydrocarbon contamination in shallow water bearing strata. Any of these situations (unless properly handled) leads to a disastrous waste of oil resources. This study discusses (i) casing leaks in Kuwait oil fields, (ii) the nature of the formations opposite the leaks and their contained fluids and (iii) the field measures that can be adopted in order to avoid casing leak problems.
A Case History–Fracturing the Morrow in Southern Blaine and Western Canadian Counties, Oklahoma
Authors: Craddock D. L. , Goza B. T. , Bishop J. C.
Published: December 2007

This paper presents a case history of recent hydraulic fracturing treatments of the Morrow formation in southern Blaine and western Canadian counties of Oklahoma. Hydraulic stimulation has often been avoided in the past because of water-sensitive clays commonly found in the Morrow formation. However, recent field results by Sun show that the Morrow in this area can be successfully and profitably fractured. Included is a history of Morrow treatments in the area, a summarization of recent treatment techniques and their results. Also, an economic analysis of these results is included using two years of actual post-frac production history.
Proper Operation of Pumping Units Reduce Lifting Costs
Authors: Moriarty D. G. , Renard D. P.
Published: December 2007

The pumping unit is a significant investment and essential to the life of a producing oil well. A proper inspection and maintenance program will prolong the life of the unit and reduce production costs. Leamco Services, Inc. successfully uses the discussed simple field inspection techniques to maintain pumping units in proper working condition.
Surface Integral Schemes for Fluid Flow and Induced Stresses Around Fractures in Underground Reservoirs
Authors: Cleary M. P. , Crockett A. R. , Martinez J. I. , Narendran V. M. , Slutsky S.
Published: December 2007

abstract

The character of fluid flow in and around wellbores, cavities, and fractures in para-elastic media can significantly affect resource extraction operations in underground reservoirs. Reasonable estimations of hydraulic fracture profiles and propagation rates cannot be made without considering fluid exchange, especially for high leak-off; well production rates greatly depend on the flow rates into fractures; and reservoir properties are often strongly stress-sensitive.

In this paper, the fluid loss and the subsequent "backs tress" (i. e. induced reservoir stress) caused by it are characterized for stationary and propagating fractures, and the model is applied to three cases:

a single fluid in the reservoir and fracture; two fluids: a reservoir fluid and a fracture fluid that has penetrated some distance into the reservoir; a production model where the crack has been propped and the reservoir fluid flows out of the well.

The fluid exchange between fracture and reservoir is found by solving an integral representation of the flow in the reservoir. Since the pressure distribution in the reservoir is governed by a diffusion process, the flow out of (or into) the fracture and the backstress are rather simply calculated by integrating along the fracture the influcence function for the pressure due to each component of fluid exchange, specifying the pressure at each point on the fracture or closing the system by some other means such as solving simultaneously the flow equations in the fracture, and solving for the fluid exchange inside the integral. Then backs tress can then be found from the fluid exchange. Preliminary computational results for plane fractures have been obtained that compare well with existing special analytical and numerical solutions (e.g.,those of Cinco and Samaniego). More general results are provided for moving fractures and induced stresses, and the broader capabilities of the methodology are outlined.
A New Method for Determining the Rheology of Crosslinked Fracturing Fluids using Shear History Simulation
Authors: Craigie L. J.
Published: December 2007

A new method which incorporates shear history simulation has been developed for measuring the rheological properties of crosslinked fracturing fluids. This proven method can provide the true rheology of the working fluid which enters the fracture. These data are essential when designing and conducting treatments in low-permeability formations, in order to obtain the desired fracture geometry.

Recent research has shown that the rheological properties of crosslinked gels are dependent on the method of preparation and testing. A single formulation of a fluid prepared by two different methods can have resulting viscosity profiles which differ by several hundred percent. The new method of measuring rheology overcomes many of the previous discrepancies resulting from preparation and testing by incorporating a shear history into the procedure. This shear history is similar to the tubular shear history a fluid experiences before it enters a fracture. The shear history apparatus is a capillary viscometer consisting of a series of tubes and additive pumps for the addition of crosslinkers. The length of the tubing as well as the pump rate can be adjusted to match laminar shear rates and shear histories encountered in fracturing treatments.

The paper describes a field scale-up model which verified the results of the laboratory tests.

Correlation of field data from bottom-hole tubing pressures on several fracture treatments further substantiates the validity of the laboratory apparatus. Results are presented which show that laboratory data can now be used to predict friction pressure exerted by fracturing fluids. Perhaps more important, though, is the insight now available into the true rheology of the fluid that enters the fracture and the development of techniques for controlling this rheology.
Enhanced Oil Recovery - A Look to the Future
Authors: Holland Henry K.
Published: December 2007

Thank you, Ernie, for that kind introduction, and good morning ladies and gentlemen. Alex Massad has asked me to extend his sincere regrets at not being able to be here with you this morning. Fortunately, from my point of view, his absence is a welcome opportunity for me to address this audience of fellow petroleum engineers.

This is the age of the acronym — with good reason. Consider for example, the poor newspaper headline writer who has to fit Intercontinental Ballistic Missiles into two columns of space while including a verb and a few other modifying words to boot. Thus, we all know what ICBM means . . . or UFO — even if we've never seen one. You didn't have to see the movie; either, to know what — or who — ET stands for.

While it may not be a household acronym just yet, I know everyone in the SPE recognizes EOR, Enhanced Oil Recovery, the subject of this morning's discussion. I must honestly admit, however, I would feel more confident in writing a believable sequel to ET, than in predicting what might happen down the road for EOR. ET may have gone home, but EOR is here to stay.

With the knowledge that oil is a finite resource, the art of getting more production from each known reservoir will depend heavily on EOR and remain of paramount importance to the future of the oil industry and the United States economy. My crystal ball remains a little clouded as to the exact impact specific future applications will have due to uncertain political and technical factors. Perhaps our discussion today can blow political and technical factors. Perhaps our discussion today can blow away some of the fog and give us an outlook for recovering more of what we have already found.

For this morning's discussion, I'll limit comments to the U.S. industry. We'll take a look at what has been found, cumulative production, current reserves, and what we might logically expect in reserve additions through application of existing and future EOR technology. We will also cover some of the economic factors involved.
The Economics of Creative Financing
Authors: Capen E.C. , Casey D.F.
Published: December 2007

The oil business works off of borrowed money, some of it disguised to look like operating costs -- leases for example. Though the rules are by no means clear, sometimes the proper economic treatment requires placing a capital equivalent of the commitment at the time of signing. The procedure can significantly change the project rate of return.

Introduction

Now and then, someone comes in and announces that he has discovered the business man's equivalent to the Fountain of Youth -- a corporate money tree. The person will instruct us that his pet project (PP) need not compete for cash in the budgeting process because he has found a benefactor, Mr. S. Claus, willing to put up the money at no cost save some "small monthly payments" to be worked out later. These payments should come from PP's profits and thus represent no real drain on the company.

To be sure, we seldom see requests as blatant as portrayed above, but we nevertheless sense some misunderstandings about how to evaluate projects that have alternatives to outright purchase of goods and equipment. Has the old maxim prohibiting free lunches somehow been set aside with regard to so called creative financing? No, more likely the lunch costs more than normal, but we're not always sure who pays.

We want to examine some of the more popular financing methods to see if we can determine who owes what to whom, at least to the extent we can work our way through the somewhat arbitrary practices of the financial community. We would like to contribute to this debate and get others to join in so that we can all become better educated.
Development, Field Experience, and Application of a New High Reliability Hydraulically Powered Downhole Pumping System
Authors: Grant A. A. , Sheil A. G.
Published: December 2007

Expansion of secondary oil recovery operations both offshore and onshore and geothermal energy recovery has led to an increasing requirement for artificial lift systems. A large proportion of these systems incorporate submersible pumpsets downhole either for pumping of oil or for the lifting of water from subterranean aquifers. Many of these applications are characterised by the requirement for high horsepower installed downhole and/or, particularly offshore, installation of the pumpsets in highly deviated wells, and/or high temperature. For these applications, experience has shown that the technical difficulties encountered in the extrapolation of existing submersible electric motor pump technology are severe resulting in poor service reliability and high maintainance cost.

The authors describe the concepts incorporated, to overcome these difficulties, in an entirely new patented hydraulically powered downhole pumpset which has been developed with support from two large oil companies and the U.K. Department of Energy.

Laboratory test and field operating experience is discussed in relation to reliability objectives.

The paper reviews the range of applications for the new hydraulic drive concept in relation to existing offshore and onshore technology and also reviews the types of system and completion which will take full advantage of the features of this new concept.
Analysis Techniques for Offshore Platform Tieback Systems
Authors: Griffith D. L.
Published: December 2007

The development of offshore fields using subsea drilling templates and tie-back equipment has become an accepted method of achieving early production.

This technical paper will give an introduction to tie-back systems, present a method of analyzing them, discuss the loading conditions that affect tie-back systems, and describe a method of accounting for loading conditions during analysis.
The Application of High Volume Jet Pumps in North Slope Water Source Wells
Authors: Christ F. C. , Zublin J. A.
Published: December 2007

ARCO Alaska's pilot water flooding system for the Kuparuk Field requires 40000 to 50000 B/D (6360 to 7950 cu m/d) of fresh water from a 3000 foot (914 m) deep aquifer. The artificial lift system selected must be of proven technology, reliable in the harsh environment, easy to maintain, and compact for ease of enclosure.

The two lift systems considered were electric submersible pump and hydraulic jet pump. Pilot well tests were run using these two types of systems and will be discussed. These tests confirmed the formations’ producibility, and revealed some problems at high rates. Based on pilot test results, a system of ten specially designed 3 in. (7.62 cm) jet pumps was selected. Background on jet pumping, design features of the system, results of the tests in October 1982, and comparison with predicted performance will be presented.
Mineralogic and Petrologic Overview of Core Samples From the Dept. of Energy's Western Gas Sands Project Multiwell Experiment, Piceance Basin, Colorado
Authors: Eatough M. O.
Published: December 2007

The Petrology Laboratory of Bendix Field Engineering Corporation (BFEC) at Grand Junction, Colorado, is performing mineralogie and petrologic analyses on core samples from the Multi-Well Experi-ment (MWX) project for Sandia National Laboratories. The samples studied to date include some fluvial sands, transitional sands, and shoreline blanket sands. The sands are generally fine-grained feldspar-and lithic-rich quartz sandstones, with minimal textural and mineralogie variation. Porosity is predominantly microporosity in clays which fill secondary pore space. The primary factor limiting the permeability of these sands appears to be the clogging of the pore space by clay minerals.
Brine-Resistant Sulfonate Surfactants for Enhanced Oil Recovery
Authors: Stournas Stamoulis
Published: December 2007

One of the most severe limitations of surfactant waterflooding is the instability of the commonly employed surfactants in the usual ionic environments of oil reservoirs. A specific modification to the usual structure of sulfonate surfactants not only makes them immune to high concentrations of monovalent and divalent cations, but also enables them to act as stabilizers of the common surfactants and to displace tertiary oil in brines of high salinity and divalent ion content.
Mechanism of Polyacrylamide Gel Syneresis Determined by C-13 NMR
Authors: DiGiacomo P. M. , Schramm C. M.
Published: December 2007

Polyacrylamide gels have been used for some time to reduce water cut in production wells and control profiles in injectors. Formations up to 150°F have been treated rather routinely. Recently, interest has developed in using these gels at higher temperatures in formations containing relatively hard brines. We have investigated the changes in hydrolysis of polyacrylamide polymers and gels crosslinked with trivalent chromium with C-13 NMR. This method is a direct way to correlate changes in the gel composition with effectiveness under severe conditions.

The carbonyl carbon of the amide group has a sharp resonance at 181 ppm. As the amide groups hydrolyze, the 181 ppm resonance decreases in intensity and a second resonance appears at 184 ppm. This resonance is due to the carbon in the carboxyl ate formed by hydrolysis of the amides. Of course, the resonance is already present in partially hydrolyzed polyacrylamides, but increases in intensity as hydrolysis progresses.

In gels, crosslinked with paramagnetic ions such as chromium III, these resonance lines are broadened, but resolvable. Line shape analysis fits the spectra closely and allows integration of the intensity of each resonance. The degree of hydrolysis and changes in the degree of hydrolysis can be determined for the polyacrylamide chains comprising the gel. The increase in the degree of hydrolysis parallels the syneresis of the gels and their concommitant loss of effectiveness. The syneresis is caused by reaction of the newly created carboxylate groups with hardness ions in the brine leading to extensive over-crosslinking. This is a fundamental characteristic of polyacrylamide gels and will take place regardless of polymer source.
Simulation of Reservoir Permeability Heterogeneities with Laboratory Corefloods
Authors: Ball J. T. , Pitts M. J.
Published: December 2007

A variety of enhanced oil recovery techniques have been proposed to alter reservoir permeability variations and effectively sweep lower permeability zones with high oil saturations. The application of these techniques must be preceded by a careful design of the fluids used. Conventional laboratory coreflooding can answer many questions concerning the flow properties of each fluid in reservoir rock but, in general, the core being tested represents one of potentially several available permeability ranges. Work has been completed and is described in which cores of three different permeabilities are flooded simultaneously. Diversion of fluid from one core to another can be followed in order to test the effectiveness of various enhanced oil recovery agents in this application.

Initial tests were completed in radial Berea sandstone cores using an alkaline sensitive crude oil from southern California. The ability of the multiple core technique to generate relative flow and resistance factor data is demonstrated. Tests of alkali, polymer and alkali/polymer combinations are presented. Results indicate that, while polymer addition to the alkaline agents increases overall tertiary recovery, improper polymer selection may result in efficient recovery only from high permeability zones. In order to effectively reduce residual oil saturation in lower permeability zones, additional polymer design considerations are needed.
Chemical Interactions of Aluminum-Citrate Solutions with Formation Minerals
Authors: Walsh M. P. , Rouse B. A. , Senol N. N. , Pope G. A. , Lake L. W.
Published: December 2007

In order to test the effectiveness of complexing agents for in-depth cross-linking and mobility control in polymer and waterfloods, we investigated the transport of aluminum citrate solutions in sandstone and limestone cores. The study was prompted by experimental observations indicating that crosslinking attempts cause plugging of the inlet end of core sections unless special precautions were observed. The plugging was caused by poor transport of the aluminum citrate solutions, which, in turn, was caused by precipitation of aluminum hydroxide in limestone cores, and of both aluminum and ferric hydroxide in sandstone cores. The formation of these precipitates, and the poor transport of the aluminum citrate solution was confirmed experimentally and modeled quantitatively by a geochemical flow simulator.

We then used the flow simulator to design injected solutions that would avoid precipitation, generally by raising the injected pH and by using a larger citrate to aluminum ratio. By using these solutions the precipitation could be avoided, and the aluminum citrate could be transported in an unretarded fashion. Polymer cross-linking treatments using solutions designed to eliminate precipitation generally showed more uniform mobility reduction, and an absence of the plugging observed in the first set of flow experiments.
SrSO4: The Basic Solubility Data
Authors: Vetter O. J. G. , Vandenbroek Ita , Nayberg Julia
Published: December 2007

Strontium sulfate solubilities may play a role in many disciplines of science and engineering. For example, strontium sulfate forms scale in oil and/or geothermal fields which are frequently accompanied by other sulfates of alkaline earth metals. Strontium sulfate solubility data, which is necessary for dealing with the scales, is rather limited in the literature.

If one is dealing with an oil field or geothermal scale or any other precipitation problem related to the strontium sulfate solubility, it would be essential to use a reliable and comprehensive data base. Existing data bases for strontium sulfate solubilities are unfortunately limited to relatively non-hostile thermodynamic conditions. In order to update this data base, a rather comprehensive study of strontium sulfate solubility under a variety of conditions was undertaken.

The present paper is a summary of the laboratory measurements of the solubility of strontium sulfate as a function of temperature (25-150 °C), NaCl concentration (0-25 wt%), CaC12 concentration (0-4 wt%), and MgC12 concentration (0-4 wt%). A radioactive tracer technique using the Sr-90 isotope has been used for measuring the solubilities. Some of the SrSO4 solubility data determined has been cross-checked by using the S-35 isotope. In addition to solubility studies, several perliminary experiments have been conducted to determine the effectiveness of radioactive tracer methods over other existing analytical methods.

The paper focuses on the significance of the solubility obtained as it relates to the solubility of other alkaline earth metal sulfates. In addition, the applicability of the radiotracer method for the solubility determinations is discussed.
Hydrogen Sulfide Preplanning for Drilling Operations
Authors: McCall W. A.
Published: December 2007

Operators planning drilling operations in the Rocky Mountain Region must often consider the possible dangers and complications which could result from encountering hydrogen sulfide while drilling.1 Many types of services and equipment are currently available to operators yet few objective guidelines exist to assist the operator in choosing appropriate safeguards. Because both overprotection and under-protection are costly, some objective means of decision making are required.

This report presents a logical and generic approach to aid the operator in making consistent, cost effective decisions. Variables related to the health and welfare of workers and residents are con- sidered, as are factors involving maintenance of property. A decision tree approach is used to priori- tize considerations. Legal, ethical and cost considerations will be evaluated together with optional individual preferences for procedures and equipment to achieve maximum safety on location at reasonable expenditure.
STRESSFRAC—A New Dimension in Well Treatment
Authors: Simmons A. L.
Published: December 2007

This paper deals with development, application, and results of using this downhole gas generator. The inventor of the tool, Henry Mohaupt, also invented jet perforating as we know it today. Prior to that he invented the bazooka.

Tried in over 3500 wells, the process is gaining acceptance from several operators in the Rockies. Its uses in completion, reservoir evaluation, as a primary treatment for hydraulic fracturing or acidizing, and in remedial stimulation are just beginning to be understood. Accurate fracture lengths are at present not well enough defined, but prior tests indicate penetrations of approximately 45ft (13.7m) at a depth of 6000ft (1.83km).

Results of the procedure on various formations and its applicability to untried zones are discussed.
Current Status of Nonthermal Heavy Oil Recovery
Authors: Alikhan A. A. , Farouq Ali S. M.
Published: December 2007

Heavy oils are an important resource worldwide, and yet two-thirds of the heavy oil deposits cannot be exploited by means of thermal recovery methods, because the effective energy production approaches energy input for reasons of formation thickness, depth, oil saturation and/or porosity. In such instances, especially if the heavy oil is not too viscous (below about 1000 centipoises), it may be economical to employ non-thermal recovery methods. These include polymer flooding, alkaline flooding, carbon dioxide (gaseous) floods, solvent floods, and other more specialized recovery methods, such as emulsion flooding, and combination techniques.

This paper discusses non-thermal heavy oil recovery methods, based upon their application in the field. The processes and their mechanistic features are briefly discussed in the light of laboratory observations, which tend to be more optimistic than field results.

The field tests, using non-thermal recovery are tabulated. This tabulation gives not only the reservoir rock and fluid characteristics, but also the reported test results, and any information on the economics of the respective tests. The salient injection-production data of each test are also considered. The data presented is designed to aid engineers in evaluating prospective field tests of the recovery methods considered.

It is shown that at the present time carbon dioxide (gaseous) seems to hold considerable promise for the recovery of moderately viscous heavy oils. While laboratory results are encouraging, field experience using this technique is still limited. Several field tests in progress would provide more information in the next few years. The remaining methods have met with mixed success. One of the more widely favored methods - caustic flooding - has performed rather poorly in the field. It is concluded that given somewhat special conditions, nonthermal heavy oil recovery methods may be applicable to reservoirs considered to be marginal from the thermal recovery standpoint.
Formation Evaluation by Reservoir Rock and Fluid Sample Analyses
Authors: Rose Walter
Published: December 2007

Reservoir rock and fluid sample testing is one of the traditional modes for formation evaluation, but like others (e.g. wireline geophysics, well testing, subsurface geologic mapping, etc.) it is one that has benefited from recent advances in laboratory methodologies and instrumentation. Before the final chapter on this subject is written, however, some enormous problems have to be faced and resolved. For example, it is mentioned in this paper that a major obstacle to obtaining credible formation evaluation information from core and fluid studies has to do with the integrity of the sampling procedure itself. Are enough samples routinely taken? Are they big enough, representative enough? And how can the in situ reservoir characteristics be maintained and sustained prior to and during subsequent laboratory testing? In the final analysis, however, it is shown that even when the various sampling problems are solved, questions will still remain about how to strike a cost-effective balance between getting rough information quickly and cheaply versus resorting to more expensive and time-consuming laboratory testing as the way to reduce noise-to-signal problems in data recording and interpretation.
Prediction of Abnormal Pressures in Wyoming Sedimentary Basins Using Well Logs
Authors: Evers J. F. , Ezeanyim Richard
Published: December 2007

Abnormal formation pressures are present in lower tertiary - upper cretaceous formations of Wyoming sedimentary basins. Calibration curves for predicting pore pressures were established for these formations using conductivity and acoustic log responses from existing wells in these basins.

Comparison was made between the predicted pore pressures using the calibration curves and some actual measured pressures. It was found that the calibration curves had an accuracy of pore pressure predictions of approximately ±0.03 psi/ft of depth, or 300 psi at depths below 10,000 feet for the comparison well.
Some ‘High-Impact’ Corrosion Problems in Production Operations
Authors: Turpin M P , Young I , Abbott J , Kamath A
Published: December 2007

In a hostile environment such as the North Sea, corrosion problems of all kinds manifest themselves with monotonous regularity, despite considerable efforts to prevent and control them.

This paper is presented with the intention of illustrating the various kinds of potentially "high-impact" corrosion problems which we are being faced with and the techniques employed to assess and monitor these problems as a means of identifying subsequent action.

The large sums of money involved, whether spent to rectify a potential problem or incurred as a result of not identifying a problem early enough, mean that assessment and monitoring are very important aspects of our operations.
Utilisation of The Peng-Robinson Equation of State in Multiphase Flow Pressure-Gradient Calculations in Oil and Gas Wells
Authors: Sutton R P , Farshad F F
Published: December 2007

An evaluation of utilising the Peng-Robinson Equation of State to perform the PVT calculations required for pressure-gradient calculations in oil and gas-condensate wells is presented. The evaluation is made using a total of 50 well tests representing 30 different wellstream molar compositions. Twenty-five of the fluid systems are gas-condensates with liquid yields ranging from 5 to 194 bbls/MMcf. The remaining five compositions are from black-oil fluid systems with gas-oil ratios ranging from 481 to 2,026 scf/bbl. The compositional and well-test data are summarised in Tables 3 and 4.

Multiphase flow pressure-gradient (MFPG) calculations were made using nine well-known correlations. PVT properties required by these correlations were derived using compositional and more traditional methods. The results of the calculations were compared with measured data to ascertain the suitability of the various methods for handling PVT calculations along with the overall general applicability of the MFPG correlations.

This paper is not intended to provide an in-depth discussion of the various pressure-gradient calculation methods as the information is readily available from several gradient calculations and some general observations made as a result of the calculations.
Gaslift Optimization - Claymore Field
Authors: Kleyweg D , Tiemann W D , Dalziel S G
Published: December 2007

The Claymore field has been developed with a single 36-slot integrated platform. Wells drilled from the platform are deviated up to 70° to reach reservoirs in the Lower Cretaceous Sands, the Upper Jurassic Claymore Sands, the Zechstein Limestones and Dolomites and the Carboniferous Sands. Produced fluids from the reservoirs vary considerably in PVT properties, but are all of the low-GOR type.

Gaslift was selected as the artificial-lift system for the field and compressors were installed with a total throughput of 200 MMSCF/D at a discharge pressure of 1,600 psig.

Wells are typically completed with 5-1/2" plastic-coated, premium threaded tubing equipped with side-pocket gaslift mandrels. The gaslift design and mandrel spacing are based on 12,000 BF/D with a 50% watercut using up to 10 MSCF/D of gaslift gas. Because of the high gas rates needed, dual-valve stations (two mandrels one joint apart) are used. Fig. 1 shows such a well completion.
Topside Facilities Design for Hutton TLP
Authors: Wingate Peter M , Hasz John W , McGee Michael D
Published: December 2007

The Hutton North Sea field is to be developed using the world's first commercial Tension Leg Platform (TLP). This paper explains how the choice of a TLP, with its dynamic behaviour and structural configuration, affected the design of the topside facilities. The problems faced by facilities engineers are described as are the methods used to resolve them. The nature of the problems described are general to TLPs, consequently the material presented is applicable to designs of the future.
The Design, Construction & Operation of the Helicopter Underwater Escape Trainer
Authors: Urquhart A E
Published: December 2007

During the early days of helicopter operations, mainly in the Royal Navy, some aircrew lost their lives after a controlled ditching or a heavy landing onto the sea, when they became trapped in an aircraft which capsized and sank. The subsequent inquiries often proved that some of the victims were fit enough to have effected an escape and the cause of death was usually attributed to disorientation during the capsize and sinking. In some cases, the problems associated with disorientation were exacerbated by the accidental or positive operation of inflatable lifejackets, which made escape from the submerged helicopter virtually impossible.

Concern was such that helicopter underwater escape training facilities were built by the Royal Navy. The Royal Navy's commitment to helicopter underwater-escape training is shown by the fact that all helicopter aircrew and others whose duties cause them to fly regularly, must complete initial helicopter underwater escape training followed by refresher training every two years. (Reference No. 1)

Civil helicopters hopefully are not likely to be subjected to the possibility of being shot from the skies and descending in an uncontrolled manner. Should a civil helicopter have to ditch, due to some mechanical or electrical failure, it is reasonable to predict that it may do so in a controlled manner, with the pilot either taking the positive decision to ditch the helicopter, or being forced to do so.
A Comparison of the Performance, Cost and Environmental Effects of Diesel-Based and Low-Toxicity Oil Mud Systems
Authors: Hinds A A , Smith S P T , Morton E K
Published: December 2007

The paper reviews and analyses performance, toxicity and cost data generated during the development and field application of a low-toxicity (LT) oil mud system. During the development phase approximately twenty "white mineral oils" were studied and evaluated as prospective diesel-oil substitutes. Their mud-formulating properties and toxicity to a variety of aquatic species were compared with those of diesel oil. The LT oil muds, to date, have been used successfully to drill over seventy wells.

The advantages of drilling with an oil-based mud are well documented. These include improved well bore and formation stability, high lubricity, fluid stability at high temperatures and pressures, corrosion protection and tolerance to contaminants. However, the LT oil muds offer an additional advantage, namely, environmental compatibility, not hitherto available, with diesel-based systems.

Government regulations restricting the discharge of oil and other toxic substances into the marine environment have precluded the use of diesel-oil systems in certain areas. Further, operators have often found cuttings-wash systems to be ineffective for removing diesel mud from cuttings. Recently, several governments have approved the direct discharge of LT oil mud cuttings which makes these systems cost effective and thus highly attractive.

The white mineral oils were found to contain significantly less aromatic hydrocarbons than diesel oil, were less toxic and fluoresced to a lower degree.

Kinematic viscosities ranged from 6.6 to 1.0 at 40°C providing great flexibility in adjusting the rheological properties of the mud to meet specific conditions. Approximately eleven oils have been used in mud formulations and successfully employed in drilling wells.

The LT oil muds were found to perform as well as diesel-based systems with a marked improvement in penetration rate in many cases.

Toxicity studies were conducted by several reputable laboratories in Europe and the United States. The results indicated that the non-toxic muds had LC50'S which ranged from 10,000 ppm to 50,000 ppm for the brown shrimp Crangon crangon; and 100,000 ppm for the plaice, Pleuronectes pletessa. Corresponding results for the diesel oil systems were 160 ppm C. crangon and 4,700 ppm P. platessa. Several of the LT systems have been approved by European governments for the direct discharge of unwashed cuttings.
Better Turbodrilllng Can Give Dramatic Reductions in Drilling Costs
Authors: de BRUIJN H J
Published: December 2007

A field performance analysis of turbine-driven bits assumes that the rate of bit penetration is roughly proportional to the mechanical power available from the turbine. The variations in bit performance can then be explained by variations in turbine power output, which is a function of torque and rotational speed and thus is controlled by weight on bit (WOB). The data show that natural diamond bits give their best performance at high WOB, whereas polycrystalline diamond compact (PDC) bits perform best at low WOB. The data further suggest that at optimum WOB the rate of penetration could be improved by 200–300%.

A turbine tachometer could enable drilling to be performed at exactly the rpm at which the turbine develops its maximum power and thus gives the highest rate of penetration. Calculations show that the cost per metre drilled may thus be reduced by as much as 50%.

The drilling rate can further be increased by improving the hydraulic capabilities and efficiency of the rig, using:

Larger drillpipe, e.g. 5 1/2" instead of 5", to take advantage of the larger bore. Drill collars and Hevi-Wate drillpipe with larger inside diameter. A minimum amount of drill collars and Hevi-Wate drillpipe for the maximum WOB. Higher standpipe pressures (max. 500 psi).

The reduction of frictional losses in the hydraulic system of the rig thus obtained, together with the higher standpipe pressure allowed, would enable the operator to run turbines with more stages and to circulate more mud, resulting in up to 50% higher turbine output. Calculations show that in this way a further reduction of perhaps 25% can be obtained on the cost per metre drilled.
Underwater Manifold Centre - Drilled- Cuttings Disposal System
Authors: Biddlestone P A
Published: December 2007

During the construction of the Central Cormorant Underwater Manifold Centre (UMC), it was recognised that the cuttings produced during the drilling of template wells would interfere with UMC operations, if deposited on top of the structure.

A dual system was developed and installed on the Stadrill (the unit planned to drill the wells) to remove the cuttings from the rig to the seabed away from the UMC.
Development Of A Diverless Subsea Flowline And Control-Line Connection System
Authors: King C R , Ostocke H D , Best McEvoy M J A
Published: December 2007

The laying and coupling of subsea flowline bundles is an important feature of subsea oil and gas production systems. A critical part of the operation is the final pull-in, alignment and connection of the flowline to fixed seabed production structures.

This paper traces the development of equipment to accomplish the diverless connection of flowlines and control lines and the field experience to date.
An Investigation of a High-Strength Proppant Tail-In at McAllen Ranch Field
Authors: Lindley B. W. , McGhee B. F.
Published: December 2007

Producing deep, geo-pressured, extremely tight gas reservoirs which have received massive hydraulic fracture treatment, creates severe crushing stresses on proppant placed in the fractures. Several high strength proppants are available on the market. While these proppants are superior to frac sand they are considerably more expensive. The question of the producer is one of pure economics. In some cases economics of a prospect may be marginal ; therefore, the operator considers alternative measures. One alternative is modification of the proppant schedule to place a regular strength proppant deep in the fracture and a high strength proppant next to the wellbore where closure stresses will be greatest.

This paper discusses the evaluation of proppant placement in a massive hydraulic fracture treatment "tail-in" technique. The term "tail in" is used to describe the final proppant stage of a multi-stage fracture treatment. A new evaluation method was developed to determine placement of this tail-in stage. For this new method the leading stages of proppant laden fluid were tagged with a long half-life isotope, 74 days. The tail-in of proppant laden fluid was tagged with a short half-life isotope, 8 days. Comparison of calibrated radiation logs recorded before and immediately after fracture treatment define the placement of proppant tagged with both isotopes. A third radiation log, recorded at the appropriate time measures decreases in radiation of both isotopes. Processing data from these three logs in a mathematical model enables calculation of proppant placement during treatment.

Four wells were treated in Forest Oil Corporation's McAllen Ranch Field, Hidalgo County, Texas. Of these four wells, one was treated with a "tail-in" technique and the other three with a 100% bauxite simulated "tail-in" technique. In these four wells, the proppant was tagged with two different radioactive isotopes to determine If the "tail-in" fraction was placed next to the wellbore. In all four wells, the evaluation indicated both proppants next to the wellbore. Factors causing this were diversion to different members during treatment and override of the leading proppant. Without proper placement of the bauxite "tail-in", extreme closure pressures near the wellbore would crush the regular strength proppant and loss of reserves would result.

Post-frac buildups were performed on two wells which had been subjected to approximately the same closure pressure. The well with 100% bauxite had much greater fracture flow capacity, than did the well with a tail-in treatment.

Experience gained from these four wells indicate that the "tail-in" technique of stimulation was not successful at McAllen Ranch Field.