bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Oxygen on Fracturing Fluids
Authors: Walker Michael L. , Shuchart Chris E. , Yaritz Joseph G. , Norman Lewis R.
Published: December 2007

The stability of polysaccharide gels at high temperature is limited by such factors as pH, mechanical degradation, and oxidants. Oxygen is unavoidably placed in fracturing fluids through dissolution of air. To prevent premature degradation of the fracturing fluid by this oxidant, oxygen scavengers are commonly used.

In this paper, the effects of oxygen and various oxygen scavengers on gel stability will be presented. Mechanical removal of oxygen resulted in surprisingly stable fracturing gels at 275°F. However, chemical removal of oxygen gave mixed results. Test data from sodium thiosulfate, sodium sulfite, and sodium erythorbate used as oxygen scavengers/gel stabilizers showed that the efficiency of oxygen removal from gels did not directly coincide with the viscosity retention of the gel, and large excesses of additives were necessary to provide optimum gel stabilization. The inability of some oxygen scavengers to stabilize the gel was the result of products created from the interaction of oxygen with the oxygen scavenger, which in turn, produced species that degraded the gel. The ideal oxygen scavenger should provide superior gel stabilization without creating detrimental side reaction products. Of the materials tested, sodium thiosulfate appeared to be the most beneficial.
Chemical Characterization of Fluids and Their Modelling With Respect to Their Damage Potential in Injection on Production Processes Using an Expert System
Authors: Thomas L. G. , Albertsen Manfred , Perdeger Asaf , Knoke H. H. K. , Horstmann B. W. , Schenk Dietmar
Published: December 2007

Deep groundwaters, esp. oil field waters, from different sedimentary basins in Germany were characterized and evaluated with respect to their damage potential in production and injection processes. Geochemical modeling with different computer programs (PHREEQE, PHRQPITZ, SOLMINEQ etc.) was used to evaluate fluid-rock-interactions as well as their damage potential during operation processes. The geochemical program PHREEQE was integrated in an expert system (XPS FROCKI) for the evaluation of operational problems (scaling, fines mobilization, reduced permeabilities) in production or injection wells.
Thermodynamic Modelling for Prediction of Asphaltene Deposition in Live Oils
Authors: Cimino Roberto , Correra Sebastiano , Sacomani P. A. , Carniani Carlo
Published: December 2007

Original phase equilibria data on asphaltenic mixtures show that the principal modellistic approaches described in the literature do not accurately reproduce asphaltene phase behaviour. A new, more reliable modellistic approach is proposed in this paper, and a procedure for predicting the stability of asphaltene solutions is outlined. Application of the new model to two oils gives satisfactory results when compared with field observations.
Development and Application of Accurate Detection and Assay Techniques for Oilfield Scale Inhibitors in Produced Water Samples
Authors: Graham G. M. , Sorbie K. S. , Boak L. S. , Taylor K. , Blilie L.
Published: December 2007

In the application of chemical inhibitors in field squeeze treatments for the prevention of sulphate and carbonate mineral scale formation, it is very important that the chemical species involved can be accurately assayed. When the inhibitor concentration drops below a predetermined threshold level for scale inhibition (Ct) then the well may need to be resqueezed. The accurate assay of scale inhibitors down to concentration levels of a few ppm in real field brines can be a difficult task.

In this paper, we examine a number of interferences which often make assay techniques very difficult to apply in field produced brines. The inhibitors examined in this work include phosphonates (PH), polyacrylates (PAA) and phosphino-polycarboxylates (PPCA). The main objective of this work is to develop suitable pre-treatment/purification techniques which allow the standard wet chemical techniques to be applied effectively after appropriate modification. Successful techniques - all based on careful modification of existing methods - have been developed by which these common inhibitors can be assayed very accurately at ppm and sub-ppm levels in a variety of North Sea field produced waters. This paper examines some of the major problems and interferences associated with poor analysis and introduces modified methods which can be applied in the field without the use of expensive equipment. It is also shown that different detection methods can often be employed in order to avoid more extensive clean-up strategies. Finally, instrumental methods such as ICP analysis (commonly used for phosphonates) are examined and pre-treatment methods are developed which allow phosphino-polycarboxylic acid based inhibitors to be assayed very accurately by this method. The results from an independent assessment by a North Sea operator, using spiked field produced water, are also presented as an independent verification of the accuracy of the techniques which have been developed in this work.
Hydrophobically Associating Terpolymer and Its Complex With a Stabilizer in Brine for Enhanced Oil Recovery
Authors: Lijian Dong , Biao Wang
Published: December 2007

This paper relates to tertiary recovery employing a polymer thickened aqueous drive fluid or mobility control fluid, more particularly, this paper relates to a novel type of thickening agent named AST agent for drive fluid composed of a hydrophobically associating terpolymer (PAAE) and a stabilizer (AN).

AST thickening agent exhibits good thermal stability (at 100°C, thermal aging in 33000 mg/l brine) and electrolytic tolerance (salinity ranging from 16500mg/l to 66000 mg/l) and good resistance to shear relative to the conventional water-soluble polymers such as polyacrylamide, acrylamide/acrylic acid copolymer etc., and furthermore, AST agent has some surface activity.

Many laboratory experiments have been shown that AST thickening agent could be considered as an advanced one in comparision with the conventional water-soluble polymers. Especially AST thickening agent is more suitable for a mobility control fluid in the hostile environment in subterranean formations such as in high salinity and high temperature formations.
Development of a Flow Injection Analysis Method for the Determination of Acrylamide Copolymers in Oilfield Brines
Authors: Taylor K. C. , Burke R. A. , Nasr-EI-Din H. A. , Schramm L. L.
Published: December 2007

An automated method for the determination of acrylamide polymers by flow injection analysis (FIA) has been developed and optimized for routine use. The method has been extensively tested for interferences common in oilfield brines. Potential interferences were examined from Na+, Ca2+, Cr3*, Al3+, Zr3*, NH4+, Cl-, OH-, CO32-, sample coloration, and commonly used surfactants. The analysis is specific for amides, and the sensitivity to concentration of amide groups in the polymer was shown to be constant as the degree of polymer hydrolysis was varied. The range of the method is 0.1 to 100 mg/L. Sample throughput is 30 samples/h with triplicate analysis. Relative standard deviations of 0.2% are readily obtained from standard solutions and 0.5% from complex samples (at 50 mg/L). The method is applicable to the determination of aqueous, acrylamide-based polymers in process streams, surface waters and oilfield brines.
A Study on Synthetical Relieving Plug Agent for Steam Huff-puff Wells in the Watersensible Formation
Authors: Biao Wang , Yunxin Cheng , Yinxue Jian , Zimian Hu
Published: December 2007

A great quantity of crude is heavy crude oil which has been produced by using steam huff-puff method in Liaohe Oil Field. This kind of crude contains a lot of resin-asphaltene and possesses the property of very high viscosity (4537 mPa. s at 50°C) and specific gravity (0.9568 — 0.9611). The formation is not only very sensible to water, but also damaged by fluids of drilling mud. Through injecting steam, the production rate was still very low and duration of steam huff-puff was very short because of plugs which were formed by clay swelling and the residual hydrocarbon that produced by volatilization of light fraction of heavy crude around wellbore.

This paper offered a synthetical relieving plug agent which is a mixed fluid, containing organic mixed solvent, inorganic acid, surfactant and other additives. The synthetical relieving plug agent (ARP — 8801 and BJ — 30) has been successfully used in 37 wells in Shuguang No. 48 union, Liaohe Oil Field since April 1989.

According to the statistical data, obtained from 33 experiment wells, it has been sown that the ARP — 8801 and BJ — 30 synthetical relieving plug agent has excellent relieving plug ability for the heavy crude wells of using steam huff-puff method in watersensible formation. The production rate per well was increased on an average from 0—8.6tons/day (before treatment) to 6.0 — 26.7tons/day (after treatment). The duration of steam huff-puff was increased on an average from 121 days (before treatment) to 218 days (after treatment). The oil/steam ratio increased from 0.41 (before treatment) to 1.17 (after treatment). The cumulative incremental oil production has reached 41704 tons.

The application in oil field proved that the method, offered by this paper, is a very nice stimulation treatment for heavy crude wells of injecting steam in the watersensible formation.

The mechanism of relieving plug is discussed in this paper also.
Research On the Preparation of Sodium Asphalt Sulfonate and its Mechanism of Fluid Loss Control for Drilling Fluids
Authors: Shen Qin-chang , Xian Tao , Yu Banje
Published: December 2007

A process for producing sodium asphalt sulfonate with gaseous sulfur trioxide has been developed with a systematic study of the main parameters which have influence on the performance of the products. After a description of a spectrophotometric method. The content of asphalt sulfonate in aqueous solutions and the adsorption of those products on British evaluation clay have been determined. The measurements of electric conductivity and surface tension for aqueous emulsions of the asphalt sulfonate have also been conducted. It is concluded that the adsorption on clays as well as the emulsification in aqueous solution are the two essential factors for asphalt sulfonate to reduce fluid loss.
Skid Mounting an 1100 Horsepower Turbine Compressor Station
Authors: Koskimaki C.M.
Published: December 2007

Skid mounting compressor stations for portability will result in a minimum amount portability will result in a minimum amount of wasted material and additional costs should the relocation of this station become necessary. Mountain Fuel Supply Company has recently skid mounted a remote control, completely automated 1100 horsepower turbine compressor station and installed it at a remote location south of Vernal, Utah.

The turbine compressor unit, piping, automatic valves, regulators and the unit controller are mounted inside of a building as one integral unit on a single skid; while the plant generators, boiler and station controller are mounted inside of another building on a second skid; and the microwave system and building are mounted on a third skid.

The yard piping and metering are the only part of this station which are not Portable. Each of the three skids can be Portable. Each of the three skids can be wenched onto a flatbed truck and moved to a new location with relative ease with only a minor amount of interconnecting piping and wiring necessary to complete the relocation.

Introduction

Skid mounting equipment for portability has become increasingly popular with industry in recent years. The obvious advantage for making anything portable is in the cost savings when and if the particular piece of equipment should ever be moved. An additional advantage is in being able to do most of the fabrication under ideal conditions in a machine shop rather than at some distant location.

With these factors in mind, Mountain Fuel Supply Company has skid mounted a completely automated, remote control, 1100 horsepower turbine compressor station along with all of the necessary auxiliary equipment and have installed it at a remote location south of Vernal, Utah and east of Bonanza, Utah.

FUNCTION AND CONTROL

This compressor station was installed for the purpose of maintaining a 500 Psig contract pressure at Bonanza, Utah, the beginning of our southern pipeline going into Orem, Utah.
The Friction Measuring Tool: Real-Time Estimates of Sandface Pressure During Fracture Treatments
Authors: Graham R. L. , Hill D. G. , Amick P. C. , Shaw J. S.
Published: December 2007

This paper describes a Friction Measuring Tool (FMT) and how it is used to estimate pressure loss from friction in the wellbore while a foam fracture treatment is being pumped. Combined with standard surface equipment, such as densitometers, flowmeters, and pressure transducers, this tool (located on the surface) offers real-time estimates of bottomhole treating pressures during the fracture treatment. Field examples are presented comparing calculated bottomhole treating pressures, based on the FMT, to actual pressures measured with downhole electronic pressure gauges (installed in the casing just below the treated zone) during stimulation treatments.

In addition to the provided field examples which verify application of the FMT, the theory and mathematical background underlying the use of the FMT are described. Construction of the tool, actual use in the field, and trouble-shooting are also presented. This tool is also applicable to foam for coiled tubing operations or stable foam drilling.

Development of the FMT is one product of a cooperative research program sponsored by the Gas Research Institute (GRI) where one of the broad research objectives is improved stimulation techniques.
Two New Design Tools Maximize Safety and Efficiency for Coiled Tubing Pumping Treatments
Authors: Gary S. C. , Walton I. C. , Gu H.
Published: December 2007

This paper describes the use of two new computer tools to assist the engineer in the design and evaluation of coiled tubing (CT) pumping treatments. Sand fill cleanouts and nitrogen kickoffs continue to comprise the majority of the operations performed by CT; however, the ability to design and evaluate jobs of this type has been limited for many years to simple steady-state calculations and general rules of thumb, both strictly applicable to vertical wells. Using these tools and an engineering design methodology, these treatments can be performed in the most efficient manner possible. The tools optimize the fluids, rates and penetration schedules by considering the effect of deviation on particle transport, reservoir influx or leakoff or both, mixing of gases in the wellbore, and other aspects of the operation. Additionally, by optimizing the required movement of the CT, pipe fatigue can be held to a minimum, providing safer and more cost-effective treatments. Examples that use these tools to design CT treatments are presented.
Optimal Design of Perforating Completion for Gas Well
Authors: Tang Yula , Pan Yingde , Wang Yongqing
Published: December 2007

The productivity characteristics of perforated gas well is investigated for the first time under real conditions considering drilling damage, perforation compacted zone and anisotropy in this paper. A nonlinear finite element model for non-Darcy flow in perforated gas reservoir is built to consider the effects of twelve factors on productivity ratio (PR) of perforated gas well. The nomographs for two cases are presented in this paper.

Compared with previous works, the following results are found: (I) The effects of drilling damage and perforation diameter on PR of gas well are more remarkable than that in oil well. (II) Any perforation phase may be the best or the worst as to perforating gas well, which depends on anisotropy, drawdown and that whether or not perforations are beyond drilling damage zone. (III) The increase in perforation length hardly improve PR of gas well when perforations have been beyond drilling damage zone.

The new method is suggested to predict or determine the turbulent flow co-efficient D’, total skin S, pseudo skin St’, and individual skin factors (Sp, Sd, Sdp) in perforated gas well.

The minimum underbalance required to obtain a zero perforating skin is discussed as well. Some drawbacks of the equation proposed by Tariq (SPE 20636) are analyzed and a new Reynold's number criterion is established. The critical Reynold's number for clean perforation is dependent on formation permeability.

Based on this research, the principle and the program for optional design of perforating completion in gas well are highlighted. These new concepts, results and conclusions would be of importance to both gas well perforating and gas reservoir engineering.
The Depletion Behaviour Of The F23 Gas Field (East Malaysia) - Integrated Studies On History-Matching Dynamic Data
Authors: Leong Stephanie M.S. , Ling Liew Shiew , Wong Kenneth U.S. , Heijna H.B.
Published: December 2007

Stephanie M.S. Leong,* Liew Shiew Ling, Kenneth U. S. Wong and H.B. Heijna

The F23 carbonate gas field has some 10 years of production history. Annual TDT surveys are conducted to monitor compaction and gas-water contact movements in the central part of the field. These observed gas-water contact movements were not compatible to those predicted by material balance studies. There was also a fear of preferential flank water influx which might lead to early flooding at the wells. Since these have important consequences to gas deliverability, multidiscipline studies were initiated. This paper describes the material balance, simulation and seismic work undertaken to arrive at a rigorous interpretation.

Background

The F23 gas field is located in the Central Luconia Province, some 200 km offshore Sarawak in a water depth of about 280 ft (Fig. 1). The accumulation consists of a Late Miocene layered platform type carbonate build-up with an areal extent of 22 km2 and a maximum gas thickness of over 1000 ft.

F23 is divided into five zones (Fig. 2), the peripheral flank Zone 5 surrounds the four horizontal zones (Zone 1 to Zone 4). An extensive aquifer lies at the bottom faces of Zones 4 and 5. The geology and reservoir properties in Zone 5 is one of the largest uncertainties in this study as no wells have yet penetrated this flank zone.

P. 485
Applications and Field Experience of an Advanced Delta Flow Kick Detection System
Authors: Haeusler Detlef , Makohl Friedhelm , Harris T. W. R.
Published: December 2007

A Kick Detection System has been developed especially for Slim-Hole applications recognising extreme low flow differences between flow in and flow out, and considering dynamic effects of the fluid system during different operating processes, i.e., tripping pipe, reaming or drilling.

The system provides audible and visual alarms to the drill floor, as well as fluid volume information.

In more than 25 applications onshore and offshore the system has proven its functionality and reliability by detecting differential flows of less than 15 1/min and kicks at influx volumes of less than 120 litres.
Validation of Kick Control Method and Pressure Loss Predictions on a Slim Hole Well
Authors: Dupuis Dominique , Augis Didier , Sagot Andre , Delahaye Thierry , Cartalos Ulysse , Burban Bruno
Published: December 2007

In order to validate a kick control method and a pressure loss model for Slim Hole, experiments on a pilot well were performed.

For the validation of the pressure loss model, flow parameters were varied so as to investigate all possible flow regimes.

For the kick control method, different drilling situations have been simulated. The paper underlines recommendations and operating instructions for the field.
New Field Methods Of Estimating Minimum Flow Rate Required For Continuous Removal Of Condensate From Gas Wells
Authors: Shirkovsky A.I.
Published: December 2007

Special field experiments have been made in the Cambay gas condensate field in western India to determine the minimum flow rate (MFR) required for continuous removal of liquid from condensate wells. Two new field methods have been developed for estimating MFR. The first is based on a calculation of the height of the condensate column at the bottom of the well and the minimum flow rate required to eliminate this column. The method requires data on pressures and temperatures at the wellhead and at bottom hole plus specific gravity of the gas and condensate. The second method utilizes data from a separator that operates at a constant temperature which is held fixed by flowing the gas condensate mixture through a sufficient length of buried pipe. From plots of the condensate-gas ratios in the separator versus pressure at fixed flow rates, it is possible to determine the MFR that will eliminate condensate from the well. Recent theoretical methods proposed by others do not give satisfactory results when applied to the proposed by others do not give satisfactory results when applied to the data of the Cambay field.

Introduction

Two-phase flow performance of gas-condensate wells under both steady and non-steady state conditions has received considerable attention in recent years. The theoretical aspects of such flow has been studied by several authors. In order to test these theories, one should have reliable data with sufficient accuracy but very often such data are not available.
Low Salinity Polyglycol Water-Based Drilling Fluids as Alternatives to Oil-Based Muds
Authors: Bland R. G. , Smith G. L. , Eagark Pasook
Published: December 2007

Both laboratory and well site data are presented on the use of high performance water-based drilling fluids containing chameleonic or TAME polyglycols. The laboratory results support a new mechanism for shale stabilization by these polyglycols and provide design criteria for optimizing their application. The well site data demonstrates an effective and efficient application of the design criteria for land-based drilling with a freshwater system. The field results show that chameleonic or TAME polyglycols can cost effectively replace invert emulsion and high electrolyte systems without the use of electrolytes to eliminate disposal costs and liability.
The Petroleum Industry and Environmental Concern
Authors: Hilpman Paul L.
Published: December 2007

Unchecked growth of the world's population, coupled with per capita population, coupled with per capita increases in resource consumption and waste production has given rise to anxieties about the future of mankind. The past decade has produced intensified concern for the integrity of earth's ecosystems. Although the petroleum industry has contributed much petroleum industry has contributed much toward the physical comfort and industrial might of modern society, it has also unwittingly contributed to excessive waste and environmental deterioration through its somewhat limited perspective. By action and influence, the industry can do much to ameliorate these conditions through programs of remedial engineering and programs of remedial engineering and hydrocarbon conservation.

Efforts in remedial engineering should be comprehensive enough to not only eliminate pollution of our coastal waters and estuaries by leaking wells, pipelines and tankers, but also to arrest contamination of surface water and ground water systems. Hydrocarbon conservation programs should ensure that fossil fuels (petroleum, natural gas, and coal) are conserved for uses that cannot be met by other resources. Furthermore, extraction processes employed in the future must be chosen on the basis of reserve-recovery ratios rather than the rapidity of investment returns.

Introduction

Since the dawn of civilization mankind has felt a kinship with the earth upon which he builds his homes, factories, roadways, and from which he obtains resources and energy to satisfy his ever growing needs. Rich have been the rewards for application of knowledge, but we have paid a high price for ignorant abuse of the price for ignorant abuse of the environment. On a short term basis, mankind can ignore natural laws, but nature, at a time of her own choosing, will present her bill to future generations for such liberties.

The decade of the sixties has witnessed the emergence of a broad ecological conscience within society suggesting that man is becoming more concerned about the day when he must pay his debt to nature. pay his debt to nature.
Do Shales Swell? A Critical Review of Available Evidence
Authors: Santarelli F. J. , Carminati Stefano
Published: December 2007

A vast majority of drilling problems occur in shales. The traditional explanation is that Shales swell when contacted with water. As the use of oil based muds becomes more difficult, recent years have seen a large numberof publications dedicated to the study of water/shale interaction.Unfortunately, this large body of evidence contains too many contradictions to be trusted as a sound basis for engineering. A two years long critical review of this material was therefore undertaken revealing that most experimental observations performed in the laboratory were not representative of downhole conditions as air or water vapor had been introduced in the samples, leading to capillary phenomena which have been mistaken for swelling. Further observations revealed that true swelling is unlikely to be an issue downhole. Upon contact with drilling fluids, the occurrence of mineralogical transformations affecting the shale was identified and it was further shown that such transformations will affect the mechanical response of the rock.
Preliminary Report on Effectiveness of Different Lubricants on Wear and Friction Coefficients Using Shale Medium
Authors: Hale A. H. , Albrecht M. S. , Roy Sanjit , Dzialowski Andrew , Mody F. K.
Published: December 2007

ABSTRACT*

Earlier experimentation demonstrated that the friction coefficient and wear of shale were highly dependent upon the chemistry of the drilling fluid. Since 70% of the formations drilled are shale, it was important to determine what additives might reduce wear of shale by a tool joint and/or lower the friction coefficient between a drillstring and shale. An examination has been undertaken to determine the effectiveness of various additives to alter the coefficient of friction and reduce wear on shale. This is an exceptionally important question when considering that most of the footage drilled is that of shale. Lower friction coefficients while drilling shale should improve the capability for longer-reach wells and reduced trouble costs. Reduced wear lowers the potential for key seating and thus limits costs. Because there is no relationship between wear and the coefficient of friction, it is important to identify reagents that can both lower the friction coefficient and reduce wear. The results indicate unique classes of chemicals are capable of lowering the friction coefficient and reducing wear. These chemicals can be incorporated into functional drilling fluids which are environmentally acceptable depending upon the concentration.

In addition results are shown which demonstrate the unique capabilities of applying an electric potential across a shale matrix. Experiments are described that demonstrate that the presence of an electric potential lowers the friction coefficient and reduces the wear in a variety of drilling fluids both water-based and oil-based. This reduction is sufficient to lower the friction coefficient on shale in a water-based mud to a friction coefficient similar to that of an oil-based mud.
Fracture Treatment Modifications and Bottomhole Treating Pressure Analysis in the Pictured Cliffs Formation, Rio Arriba County, New Mexico
Authors: Johnson Raymond L.
Published: December 2007

This paper describes the fracturing behavior of the Pictured Cliffs (PC) formation and evaluates the containment properties of the bounding intervals of the PC: the Fruitland formation and the Lewis Shale. Evidence will be presented on modifications to PC treatments that allowed proppant to be placed more effectively in the upper, most productive intervals of the Main PC. Bottomhole treating pressure (BHTP) analysis of modified and unmodified PC treatments will be presented in the form of history-matches using in a three-dimensional (3D) fracture model.
Continuous-Flow Gas-Lift Installation Design Utilizing Production-Pressure-Operated Valve Performance
Authors: Winkler H. W.
Published: December 2007

The variable-gradient design-line method is a widely accepted procedure for spacing gas-lift valves (GLV's) in a continuous-flow gas-lift (GL) installation. Injection-pressure-operated (IPO) and production-pressure-operated (PRO) GLV's can be used in a variable gradient designed installation. The primary purpose of GLV's is to unload a well to the desired depth of gas injection. If the installation design is based on a constant surface injection-gas pressure (pio), the GLV's must be opened by an increase in the flowing-production pressure at valve depth (ppfD) rather than an increase in injection-gas pressure at valve depth (pioD)· PPO, also called fluid-operated, valves are opened and closed by changes in ppfD.

This paper outlines in detail the calculations for a variable-gradient continuous-flow installation design procedure based on a constant pio for spacing the unloading PPO valves. The valve spacing and port size selection includes performance characteristics of PPO GLV's. A simplified method for calculating the injection daily volumetric gas rate (qgSC) throughput of an unbalanced bellows type of PPO valve on the basis of a change in and the valve bellows-assembly load rate (BIr) is given in the Appendix.
Optimum Plunger Lift Operation
Authors: Baruzzi J. O. A. , Alhanati F. J. S.
Published: December 2007

Operational conditions for a plunger lift installation are analyzed based on qualitative observations on a reduced experimental facility and simulations with a simple hydrodynamic model.

Despite many simplifications, model predictions for daily production and pressure behavior at the wellhead agreed well when compared with measurements in a real well.

A method is described to predict when it is possible to have liquid accumulation only in the tubing during the buildup period. It is shown that there is a minimum GLR to reach this desirable condition.

Sensitivity analysis for a typical well shows that for a given pressure there is an optimum afterflow time, and for a given afterflow time the smaller the pressure the greater the production.

Practical recommendations are given on how to obtain optimum conditions for a typical installation.
An Evaluation of Large Diameter Coiled Tubing for Subsurface Production Tubulars
Authors: Adams L. S. , Smith L. W.
Published: December 2007

This paper provides an economic and technological perspective for use of large diameter coiled tubing1 relative to threaded tubulars for subsurface production tubing. This new advancement in coiled tubing technology can significantly reduce the expense for purchasing and installing production tubing while increasing hydrocarbon reserve recovery and providing a safer, more desirable ecosystem interrelation.
Case Histories and Laboratory Studies of Cement Sheath Deposition Inside Casing Strings
Authors: Griffith J. E. , Osisanya S.
Published: December 2007

This paper describes recently observed problems of cement sheath deposition on the inside circumference of a casing string. Actual job parameters and several proposed causes of the cement sheath are reviewed. The probable hypothesis for the cement sheath deposition is a combination of temperature, cement retardation, large cement volumes, and the surfactant contained in the slurry. This hypothesis was explored through the use of large-scale, physical models to duplicate the actual well problem in the laboratory.

Based on test results, the principal cause of cement sheath development is surfactant in the cement slurry. Once the surfactant is removed or retarding agent is added to the slurry, the cement slurry can be successfully placed. This paper also includes a laboratory procedure that provides for timely screening of potential cement slurries to determine sheathing tendencies.
Detecting Production Tubing Leak by Time Resolved Geochemical Analysis of Oils
Authors: Hwang R. J. , Elsinger R. J.
Published: December 2007

Many multiple completion wells in the Gulf Coast often develop tubing string communication through leaks that may not be detected by changes in the production log of a well. Routine geochemical analyses of reservoir fluids, however, can provide an early indication of such problems and allow timely corrective action. This paper describes detection of production tubing leak by several time re-solved geochemical analyses of oils. It demonstrates that the geochemical technique is an effective and inexpensive tool for monitoring well performance.

The technique is also capable to quantitatively determine mixes of commingled production caused by the plumbing problem.
Case Studies Suggest a Better Approach to Analyzing Collapse of Inclined Boreholes
Authors: Guo B. , Hareland G. , Boonyapaluk P.
Published: December 2007

This paper addresses the comparison and selection of failure criteria for in-situ rocks in borehole stability analysis. Five commonly used criteria are compared with field cases for mud weight design. The result of case studies indicates that the Mohr-Coulomb criterion, Inner Drucker-Prager criterion and Middle Drucker-Prager criterion are overly conservative, and that the Outer Drucker-Prager criterion is underestimating for designing wellbore pressure to control borehole collapse. It is concluded that the von Mises criterion is more reliable than other failure criteria and should be used for borehole collapse analysis and mud weight design. Based on triaxial test data, this paper also provides failure diagrams for some reservoir rocks. These diagrams can be used as references for borehole stability analysis when similar rocks are encountered in petroleum drilling.
Effectiveness of Fluid Loss Additives in Laboratory Dynamic Fluid Loss Experiments
Authors: Charles Dawari D. , Xie Xiaopeng
Published: December 2007

A commercially available HTHP (high temperature, high pressure) dynamic filtration unit and a widely available HTHP rheometer was used to study dynamic fluid-loss behavior of uncrosslinked hydroxypropyl guar hydraulic fracturing fluid containing varying concentrations of silica flour, starch, and diesel.

New dimensionless groups were defined for the dynamic fluid-loss problem. These groups were used first to effectively correlate previously reported laboratory data and later were employed to analyze the ensuing experimental data.

Results demonstrate that low and high permeability cores require different mechanisms for fluid-loss control and that, compared to silica flour, starch may loss its effectiveness at higher concentrations.
Tests Confirm Operational Status of a Large-Slot Flow Apparatus for Characterizing Fracturing Fluids
Authors: Shah Subhash N. , Lord David L.
Published: December 2007

A large-slot flow apparatus for investigating hydraulic fracturing fluid flow and proppant transport phenomena has been jointly developed by the Gas Research Institute (GRI), the Department of Energy (DOE), and The University of Oklahoma. A series of tests were performed to confirm the operational readiness of this apparatus to perform the many functions for which it was designed. This paper describes results obtained from the verification tests, particularly in terms of the proper functioning of instrumentation and control systems under a wide range of operating conditions. Tests performed were: flow of crosslinked gels, high-temperature (200 and 225pF) flow tests, high-pressure (1,000 psi) flow tests to confirm proper operation of a unique throttling valve, effect of pressure on perforation pressure loss, and dynamic fluid-loss tests with permeable facings at 1,000 psi.

Verification tests listed above were performed and the large-scale, high-pressure, fracture-flow simulator was found to be fully functional in nearly every respect. Functionality was established by comparing flow data from the simulator to conventional viscometric results whenever possible. Some surprises, in terms of both flow cell response and fluid behavior, were found during the course of verification testing. For example, there was the discovery that crosslinked gels exhibit a slip-like flow phenomenon in the simulator. This latter phenomenon was discovered while using the variable width capability of the apparatus. A methodology was developed which allows collection of meaningful flow data in the presence of this slip-like phenomenon. An additional surprise was the discovery that there was no effect of elevated pressure on the perforation pressure loss, as some industry critics have suggested.
Flow Visualization of Flow Into 8 Point-Source Fractures II: The Effect of Fracture Non-Uniformity and Fluid Crosslinking
Authors: Clark P. E. , Zhu Quisheng
Published: December 2007

Recently, the flow of fluids into a fracture from a point source has been the subject of several different papers. Cleary and Fonseca1 first suggested that convective transport should play a major role in the placement of proppant when the flow into a fracture was from a point source. Clark and Courington2 presented data showing that for non-viscosified fluids convection was the dominant mechanism of transport. However, they showed, that for uniform fractures, viscosifying the fluid made a large difference in the transport mechanism. In a later paper, Clark and Zhu3 presented data for non-uniform fractures and viscosified fluids weighted with either salt or silica flour that showed that the presence of minor non-uniformities serve to negate the effect of convection even more than viscosifying the fluids.

In this work, we have extended the work presented in the previous two papers to high viscosity Newtonian fluids and crosslinked fluids. The experiments have all been done with various concentrations of silica flour to simulate added proppant. Both changing the nature of the non-uniformities and crosslinking the polymer solution have a profound affect on the flow into the fracture and the convective process.
Fluid-Loss Control for High-Permeability Rocks in Hydraulic Fracturing Under Realistic Shear Conditions
Authors: Navarrete R. C. , Mitchell J. P.
Published: December 2007

A study is presented on the effectiveness of different combinations of fluid and fluid-loss additives to control fluid loss in high-permeability formations under high shear rates. The impact on matrix damage and proppant-pack damage is also studied. Borate-crosslinked guars, hydroxyethylcellulose (HEC) and a surfactant water-base gravel packing fluid were investigated. The fluid-loss additive considered was silica flour. All fluid-loss tests were run in dynamic fluid-loss cells. To properly test high-permeability cores, new long core dynamic fluid-loss cells were used. The matrix damage caused by the invasion of the fluid was determined using pressure taps along the core. Conductivity tests were also run to determine the damage to the proppant pack.

Results show that the effectiveness of particulate fluid-loss additives under dynamic conditions is strongly dependent on the initial leakoff rate, which depends on the pressure gradient across the core, permeability of the core and viscosity of the invading fluid. The use of silica flour helps matrix flowback, and it has a minimal effect on proppant-pack conductivity in clean fluids (e.g., surfactant water-base gravel packing fluid). With the exception of the borate-crosslinked guar with no fluid-loss additive, the variety of fluids used in these tests (with and without silica flour) have a negligible effect on postproduction.
The Carbonate Envelope
Authors: Bigelow Edward L.
Published: December 2007

Exploratory well tests typically require timely, yet accurate log analysis from the responsible formation evaluation specialist. A rapid turnaround in the analysis is demanded due to economic considerations and decisions that are routinely made from log-derived, in-place reserve estimates. In general, in-place estimates are quickly expanded to include the reservoir's areal extent that was likely conceived from prior seismic and geological studies. Wireline data usually provide the porosity, saturation, pay thickness, and evidence of producibility that are input into reserve calculations. Core data are seldom available on exploration tests, especially in carbonate reservoirs.

A flexible algorithm defines formation resistivity factor (FR) boundaries within which log measurements from carbonates occur. Evidence shows the n exponent in carbonate reservoirs to be strongly affected by wettability characteristics and porosity type, but tolerable estimates of n can be made to obtain relatively accurate and timely estimates of saturation.
Improved Prediction of Foam Diversion in Matrix Acidization
Authors: Zeilinger S. C. , Wang M. , Kibodeaux K. R. , Rossen W. R.
Published: December 2007

Recent studies of foam-diversion processes for matrix acidization identify gas trapping during post-foam liquid injection as the key to foam effectiveness. Laboratory studies identify two degradation processes during this period: a rapid increase in mobility throughout the core, followed by a slower further rise in mobility starting at the core inlet. New coreflood results indicate that pressure gradient ∇P during the first process is insensitive to a shut-in period after foam injection but depends weakly on liquid flow rate. A small fall in gas saturation accounts for the first rise in mobility, which appears to depend on mobilization of foam bubbles (i.e., on ∇P) rather than foam collapse (i.e., on capillary pressure). The second rise in mobility appears to be due to gas dissolution in injected liquid. Therefore this transition, which is harmful to field performance, can be avoided by including a small amount of gas with the injected acid.

Process modeling illustrates that some designs that appear successful in laboratory linear corefloods can perform poorly in the field due to the geometry of radial flow. The fractional-flow approach, together with coreflood pressure data for multiple sections along the core, provides a uniquely simple and insightful framework for interpretation of laboratory results and extrapolation to the field.

The simple diversion model of Hill and Rossen1 can successfully model foam processes in which the secondary degradation of foam during liquid injection is avoided by including gas with the acid.
Economics of Research
Authors: Faull R.F.
Published: December 2007

Research has become essential to maintain the health of a modern-day, technically oriented company; yet, on a project-by-project basis, research is a project-by-project basis, research is a high-risk operation. In oil exploration and production, research is a team effort not easily separated from operations. Based upon 25-years of experience, it appears that research is resulting in a very attractive economic return.

Attempts to evaluate and select research projects by analytic approaches have not projects by analytic approaches have not been particularly successful. Reliance, therefore, must be on judgments, both technical and business, to determine total size of the research program as well as the nature and priorities of individual projects. Several factors related to spreading the risk and taking advantages of technical opportunities are reviewed.

Research demands to meet increased petroleum requirements of the future will petroleum requirements of the future will surely increase. More industry cooperative type projects seem to be one step in controlling industry costs.

Introduction

When your program committee asked that I discuss the economics of research today, I accepted the request as a challenge, knowing that it is a subject not easily settled with either straightforward analyses or broad generalizations. Research is a high-risk business with many "dry holes," and neither the selection of lines of investigation nor evaluation of results can be handled with mathematical exactness. If you came expecting me to offer some fancy formulas for doing so, I'm afraid you will go away disappointed.

The very first problem in approaching the subject of economics of research is that research is not a separable part of a complex, industrial activity. This is more or less true in any modern, technically oriented business; but I believe it is particularly so in oil exploration and production and perhaps equally so in other mineral recovery industries. In our business, research and field activities blend or interfinger almost continuously.
Production Optimization of Sucker Rod Pumping Wells Producing Viscous Oil in Boscan Field, Venezuela
Authors: Guirados Carlos , Sandoval Jose , Rivas Olegario , Troconis Henry
Published: December 2007

Production Optimization of Sucker Rod Pumping Wells Producing Viscous Oil in Boscan Field, Venezuela,

Boscan field is located in the western coast of Maracaibo lake and is operated by MARAVEN S. A., affiliate of Petroleos de Venezuela S. A. It has 315 active wells, 252 of which are produced with sucker rod pumping. Other artificial lift methods currently applied in this field are hydraulic (piston) pumping (39 wells) and ESP (24 wells).

The history of this field reveals the existence of several operational problems which preclude the optimum production of the sucker rod pumping wells. The main problems, however, are related to the hish frictional forces that arise between the rod string and the crude oil being produced since average crude gravity is 10 degrees API.

This paper presents the results of the production optimization of two sucker rod pumping wells of Boscan field producing viscous oil. This optimization has been possible due to the development of a new production scheme and the application of system analysis in completion design. The new production scheme involves the utilization of a subsurface stuffing box assembly and a slotted housing, both designed and patented by INTEVEP S. A., affiliate of Petroleos de Venezuela S. A. The completion design method and software used in the optimization study were also developed by INTEVEP S. A.

The new production scheme and design method proved to be effective in preventing the causes of the above mentioned problems, allowing the increase of oil production under better operating conditions.

Introduction

Venezuela is one of the main oil producers of the world. Many of this oil production is made of heavy oil and bitumen. In fact, Venezuela possesses the largest accumulation of heavy oil and bitumen of the world: The Orinoco Field Belt. Some other important Venezuelan heavy oil fields are: Melones, Ovejas, Morichal and Jobo located in the eastern region of the country, and Tia Juana, Lagunillas, Bachaqueros and Boscan, in the western region, around the Maracaibo lake.

Each one of this fields has particular characteristics, and operating criteria. All of them, however, have two common characteristics in relation to artificial lift of the viscous oil:

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