bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a New Concept of Steerable PDC Bit for Directional Drilling
Authors: Roberts T. S. 
Published: December 2007

Abstract
This paper describes the development of a new range of Polycrystalline Diamond Compact (PDC) bits designed to have the smooth torque response of a roller cone bit but maintain the high penetration rates and long life achievable from a PDC bit. One such design features a 360° full contact gauge ring that prevents outer cutters from biting into the formation at gauge. This restriction to lateral movement reduces bit whirl and thereby increases cutting structure life. Thus because the bit drills more smoothly, torque fluctuations are lower resulting in a smoother bore hole which provides more predictable weight transfer. These advantages result in faster penetration rates when sliding because far less time is spent orienting the bit.
Laboratory tests utilized an instrumented sub to measure bit vibration as well as weight on bit (WOB), torque and revolutions per minute (RPM). The stability of several bit designs having identical cutting structures but varying degrees of junk slot enclosure was compared. The results show the use of enclosed junk slots significantly reduced bit vibration and gave a much smoother torque response.
Several case studies are presented that illustrate improvements in the most demanding directional wells. These bits have now been used successfully on many directional wells in the North Sea, United states and Middle East. Directional drillers have commented that these innovative bits give the directional response and low reactive torque of a rock bit but with three times the penetration rates.
Bit Balling Reduction by Electro-Osmosis While Drilling Shale Using a Model BHA (Bottom Hole Assembly)
Authors: Hariharan P.R. , Cooper G.A. , Hale A.H. 
Published: December 2007

Abstract
In this paper we present further work on the use of electro-osmosis to prevent bit-balling. Indentation tests in wet clay have indicated that the process of electro-osmosis (EO) becomes more efficient in clays with lower water content. This fundamental behavior of wet clay correlated well with coefficient of friction measurements under EO, between a rotating metallic cylinder and a stationary shale sample for different types of shales. Test results have demonstrated that shales with a higher water content &gt;10%) respond to EO to a smaller degree compared to shales with lower water content (&lt;10%). Furthermore, in clay/sand mixtures it was clearly seen that the process of EO became active when the clay content exceeded a threshold value of about 10–12% by weight. This finding indicates that EO may be effective in sand/clay mixtures whereas until the present it has been believed to be effective only in clays.
We have also conducted drilling studies using a model BHA (Bottom Hole Assembly) in which a stabilizer above the bit acts as the anode while the bit is cathodic. This self contained arrangement is preferred for practical application of the technology in deep wells. Drilling tests in Pierre shale using this equipment have shown increases in ROP (rate of penetration) of 30% in roller cone bits and up to 158% in the case of PDC bits when the bit was made negative, with substantially less cuttings adhering to the bit. The greatest increases in ROP were found at the higher weights on bit. The effects of EO increased progressively as the current density to the bit was increased.
P. 913
Revised Drilling Practices, VSS-MWD Tool Successfully Addresses Catastrophic Bit/Drillstring Vibrations
Authors: Shuttleworth N.E. , van Kerkoerle E.J. , Folmer D.R. , Foekema N. 
Published: December 2007

Abstract
To date, several wells have been drilled in the Friesland/Groningen area of northern Holland. Historically, catastrophic cutter damage/failure in the 12 1/4" Triassic section resulted in inconsistent and unacceptable bit performance. Here, the Triassic is an interbedded formation containing hard dolomite and anhydrite stringers and abrasive sands. The transition from a softer to harder formation at high inclination evidently initiated bit and drillstring vibrations, thus causing premature cutter failure of the PDC bits used in the program.
This paper presents a detailed analysis of the 12 1/4" section conducted after the drilling of Well No. 1. The recommendations arising from the study concentrated on the use of a real-time downhole vibration monitoring or VSSMWD tool (Vibration Stick Slip) in combination with revised drilling practices to reduce vibrations when encountering the interbedded formation. Thus, on Well No, 2, nearly all of the 2358-m Rijnland and the hard and abrasive Triassic forrntions were drilled with one PDC bit on a rotary assembly, where previously six bits were required. The authors will illustrate the benefits of a detailed interval analysis and discuss the role of the VSS system and the dring crew in addressing catastrophic drillstring and bit vibrations.
P. 925
Experience Acquired During Deep Water Drilling and Testing of 3 Explo/Appraisal Wells in the Girassol Field
Authors: Crepin Stephan , Ybert J.L. , Foulhoux Laurent , Payer Nicolas , Chassagne Alain 
Published: December 2007

Abstract
Producing oil in deep water is one of Elf's major challenges and goals for the next century.
Elf has drilled and tested successfully 3 exploration/appraisal wells in the Angola offshore - GIRASSOL field - below 1300 m of water. The first one was drilled with a DP rig (GIR 1), the other two, ("twinwells": GIR 2A & GIR 2B) with an anchored up-graded Semi-Submersible rig. The distance between the twin- wells was 90 meters allowing the opportunity to drill them with the same anchor pattern. The batch drilling of the riserless phases 36" and 26" had permitted the utilization of only one run for BOP and riser.
Our targeted reservoir on the GIR 2A was at a vertical depth of 2850 m. It was reached in a 12–1/4" diameter phase using an OBM. A 210 m core section of very unconsolidated sands from the zone of production on the first appraisal well was recovered. Also the well was flow tested at a very high rate of production through a cased holed 9–5/8" gravel-pack. Because of the location of the appraisal target on the second well, a 750 extended reached well in unconsolidated shaly and sandy formation was employed.
Anchoring and dis-anchoring operations have been very successful.
Meticulous inspection of the BOP by a third party specialist helped to prevent leaks and lost time. The failure of the ROV when spudding GIR 2A has pointed out the importance of some side services.
Because of the very poor Leak Off Tests of the surface formations the architecture of the well remained heavy in spite of not very deep targets. A tight monitoring of the mud weight has been important.
A drilling well head with weight set tools has been used.
P. 427
Producing Lease Operations - Design of Operating and Maintenance Jobs and Related Tools and Transportation Equipment
Authors: Kelly Harold S. , Filson Rogers C. 
Published: December 2007

Abstract
This paper reviews some of the economies achieved through methods work on lease producing operations and depicts some of the tools and special transportation units that were designed and put into service to improve the efficiency of the working force, lengthen the life of the lease equipment and reduce downtime lost production.
It was found that the old general classification of pumper with broad duties including pumping operations, equipment servicing, and minor repairs could be advantageously replaced with a pumper classification limited only to operating duties on a greater number of wells, plus a properly equipped tune-up and service mechanic whose time would be devoted 100 per cent to tuneup, servicing and preventive maintenance. This reorganization of lease operations resulted in lower total labor costs, longer life of equipment and less lost production from downtime.
The regular lease surface maintenance roustabout work is also subject to organization, special equipment, and transportation units which permit a reduction in the cost of maintenance labor and improvement in the maintenance of the leases.
Time and Methods studies of producing leases in several districts were used as a basis for designing operating and maintenance jobs and for determining labor requirements, tools and automotive units needed to more efficiently perform these jobs. Follow-up methods studies were made after the jobs, methods, tools, and automotive units had been redesigned to determine whether the planned savings had actually been effected.
This paper covers three broad categories of work as they were delineated by the methods studies; namely (1) Operations, (2) Tune-up and Preventive Maintenance, and (3) Field Maintenance and Repair.
Economic and Technical Features of a Revolutionary Chemical Scale Inhibitor Delivery Method for Fractured and Gravel Packed Wells: Comparative Analysis of Onshore and Offshore Subsea Applications
Authors: Webb P.J.C. , Nistad T.A. , Knapstad B. , Ravenscroft P.D. , Collins I.R. 
Published: December 2007

Abstract
The deposition of scale, such as carbonates and sulphates, in production facilities represents a serious operational problem that can result in significant well productivity decline. Currently implemented scale control strategies can involve significant capital and operational expenditure.
Development work, involving laboratory testing and a field trial, has demonstrated the technical benefits of a revolutionary method of downhole scale inhibitor delivery. Economic analysis indicates that significant benefits can be derived for a variety of field development and well completion types. The greatest economic benefits would be realized for subsea and minimum facility installations with high intervention costs, where squeeze delivery of scale inhibitor or mechanical workover are used for scale control. In addition, major economic benefits can be realized for horizontal wells with unfavourable pressure regimes, multi- lateral type completions, multiple fractured wells, and many conventional completion types.
The new chemical delivery method offers cost reduction through reduced deferred oil, efficiency of chemical usage, and elimination of coil tubing and intervention vessel use. Economic analysis has indicated that fracturing a well and deploying proppant impregnated with scale inhibitor, is economically preferable to a strategy of squeeze treatment for some conventionally unfractured wells with high intervention costs, for example subsea wells.
An additional economic benefit of proppant impregnated with scale inhibitor (Chemflow) is increased well productivity. The benefit is derived from the combined effect of improved gel breaking, and scale inhibition during well clean-up. This has been demonstrated in laboratory testing and would appear to be confirmed by field observations.
A further benefit of applying scale inhibitor as chemically impregnated proppant is the instantaneous treatment of produced water when water breakthrough occurs. This feature avoids the formation damage that can occur before squeeze treatment mobilization. In addition, for some applications involving large fractures there is the potential for lifetime well treatment.
P. 323
Use of Perforation Tunnel Permeability as a Means of Assessing Cased Hole Gravelpack Performance
Authors: Burton Robert C. 
Published: December 2007

Abstract
This paper proposes a new method for comparing the effectiveness of cased hole gravelpacks. The new method employs effective perforation tunnel permeability as the primary indicator of gravelpack effectiveness.
Completion pressure losses in cased hole gravelpacked wells are subdivided into categories and systematically reviewed to show the relative importance of alternative design features. From this information, perforation tunnel permeability is shown to be the major determinant of completion skin and flow efficiency in cased hole gravelpacked wells. The technique is shown to be useful in both low velocity (Darcy) and high velocity (non-Darcy) flowregimes.
Field examples are used to show how this technique can be used to diagnose design flaws and improve well performance results. These examples show that effective perforation tunnel permeabilities in cased hole gravelpacked wells are significantly lower than surface measured gravel permeabilities. This has important implications for well design and remedial candidate selection.
P. 359
Effect of Sand-Grain Size on Perforator Performance
Authors: Brooks J.E. , Yang W. , Behrmann L.A. 
Published: December 2007

Abstract
A rock's compressive strength is generally recognized to be key in determining the depth of penetration for shaped-charge perforators, both for downhole formation rock as well as for artificial rock such as concrete. What is not recognized is that the size, distribution and hardness of the composite sand grain of the rock are also important parameters in determining penetration. Depending on the size of the grain, experiments show that penetration depth can be significantly affected, with penetration in coarse-grain-sands considerably reduced from that in fine-grain sands.
We present experimental results of penetration depths in concrete targets made with a wide range of sand-grain sizes, from very fine to very coarse, Results show that penetration in concrete targets made with single-size sands (very fine to gravel size) can have a range of effect of about 250%. Also included in the data set are tests made with API RP43 Section 1 targets using sands that are within the specification size but at opposite ends of the allowed tolerance. The data show a difference of at least 10% in penetration between these two limits, Finally, we discuss the practical implications of these results as regards API Section 1 testing and the expected effect on downhole rock penetration.
P. 371
Methodology of Fluid Leakoff Analysis in High-Permeability Fracturing
Authors: Ispas I.N. , Britt L.K. , Tiab D. , Valko P. , Economides M.J. 
Published: December 2007

Abstract
Hydraulic fracturing in medium and high-permeability reservoirs differs significantly from conventional fracturing, since the optimal placement of proppant requires shorter and wider fractures. The optimal fracture dimensions are achieved by executing a tip screenout design technique. Successful application of this technique assumes realistic description of the fluid leakoff process. Fracture calibration treatments (minifracs) have been used to identify leakoff characteristics. In addition to the application of data obtained from such tests (i.e. incorporation into the fracture job design) an increasingly important use is to obtain reservoir engineering parameters, such as formation permeability.
This paper is based on two methods, used for the determination of the leakoff parameters from the pressure fall-off stage of a calibration treatment. The first method is the well known technology, which we have called the Nolte-Shlyapobersky method to determine an overall leakoff coefficient. The second method is a modified form of the Mayerhofer et al technique, which attempts to de-couple the two main elements of the leakoff process: the filtercake resistance and the transient flow in the formation. For other methods concentrating more on the pressure fall-off after the fracture closes see References 3 and 5.
Field examples will be used to demonstrate the basic steps of the presented methodology. Emphasis is on limitations and possible pitfalls with suggested remedies. A detailed sensitivity analysis is presented which underlines the data quality required to determine reservoir and treatment parameters with any accuracy.
P. 493
A Coulpled Wellbore-Hydraulic Fracture Simulator for Rigorous Analysis of Frac-Pack Applications
Authors: Sherlock-Wills Terri , Romero Jean , Rajan Surya 
Published: December 2007

A Coupled Wellbore-Hydraulic Fracture Simulator for Rigorous Analysis of Frac-Pack Applications

Abstract
Frac pack stimulations have been used extensively to provide a combined treatment for well stimulation and sand control. It has been observed that treatment failure in such operations is often caused by a premature wellbore screen out. However, until now the design and evaluation of such treatments have been performed solely using fracture simulators that neglect the effect of the wellbore hardware (crossover ports, blank, screen, washpipe, etc.) on the treatment.
In an effort to address this limitation, a wellbore simulator was coupled with a fracture simulator to provide the capabilities of predicting, and subsequently eliminating, such occurrences. The fracture simulator calculates the fracturing parameters such as proppant distribution in the fracture, fracture height, and two-dimensional fluid flow. These parameters provide the boundary conditions for the wellbore simulator. Additionally, the fracture simulator was enhanced to correctly simulate fluid leakoff and tip screen out designs in high permeability formations.
The fluid and proppant flow around the screen is calculated using a pseudo three-dimensional wellbore simulator which provides a complete design and evaluation tool of frac pack treatment. The effects of a deviated wellbore, proppant bridging around the screen, proppant settling in the wellbore, and fluid flow through the screen are taken into account; in addition, the coupled simulator can model an induced wellbore screenout at the end of the treatment either due to a deliberate reduction of the injection rate or the shifting of the tool to the circulating position.
This paper shows a field example using this coupled simulator to evaluate a frac pack treatment that was terminated due to a premature screen out. The calibration test is initially analyzed following which the frac pack treatment is simulated and compared with field measurements.
P. 505
Damage Characterization and Production Optimization of the Hassi-Messaoud Field, Algeria
Authors: Allouti A. , Ziada A. , Ramses W. , Fragachan F.E. 
Published: December 2007

Abstract
The Hassi-Messaoud Field is a thick sandstone reservoir covering an area of 2000 km2. It is a flattened anticline located on the north of the El-Biod-Hassi-Messaoud elevation. This elevation is formed by a sequence of horsts and grabens contained by faults in a submeridien direction. The faults are in general SSW to NNE oriented and cross all the producing reservoir (Cambro-dovicien).
The producing reservoir is located at 3300 m and consists of four distinct formations in addition to a "zone d'alterance"(transition zone). These are subdivided into drains (producing intervals) characterized by distinct properties. Overall, the field is divided into 25 separate zones that differs in their geological and petrophysical properties and are under pressure maintenance by means of water and/or gas injection. Fig. 1 shows the field different zones and a cross section of the Cambro-Ordovicien formation.
This paper presents the successful application of a methodology to optimize production and results of matrix acidizing treatments in the Hassi-Messaoud field. The corner stone of the methodology is damage characterization. The damage is analyzed and evaluated per zone. Categories according to damage severity and frequency are presented. Among others these categories include salt deposition; scales deposition including barium sulfate, clays types, fines migration, and asphaltenes. A thorough coverage of the geology, mineralogy, petrophysical properties, formation fluids characteristics, reservoir pressure evolution and pressure maintenance, wells completions and production schemes are presented for the 25 different zones that integrate the heterogeneous Hassi-Messaoud field.
Finally, production optimization as a result of applying the methodology on matrix acidizing treatment is presented and quantified by :treatments success ratio;production gain;payout time;decline rates of wells before and after treatment andactual cost per ton of production gained.
P. 549
The Effect of the Thermal Stress on Wellbore Stability
Authors: Tang Lin , Luo Pinya 
Published: December 2007

Abstract
The thermal stress near the wellbore occurs because the temperature near the wellbore is changed by mud in well. The stress distribution near the wellbore is changed by the thermal stress, Eventually, the wellbore stability is affected. So, in this paper, first the integral equations of the thermal stress caused by varied temperature near the wellbore are derived from the thermoelastic theory. Then, the numerical computation is conducted for the thermal stress equations with the numerical results simulated for the temperature field near the hole. The plots of radius thermal stress distribution is obtained as a function of time. Further, the thermal stress is stacked with the pure mechanical stress near wellbore. Finally, the effect of the thermal stress on the wellbore stability is analyzed by use of the Mohr-Coulumb criterion for the any drilling condition and any time. The simulated result shows that the tangential and axial thermal stress on the holel formation interface may make the total effective stress to decrease on it below some point of section, and make the total effective stress to increase up some point. It is an important influence on the stress distribution near the wellbore. Therefore, the theories and simulated results in this paper have a guiding signification for the wellbore stability in the high temperature well and for the recovery of the production, such as the fracturing, injection, and thermal production.
P. 85
The Fracturing Technique to Limit Hydraulic Fracture Height Growth Put into Effect
Authors: Liu Shuzhi , Ren Shuquan , Zhao Jinzhou , Yang Liangxian , Wang Qingxiang , Chen Shu 
Published: December 2007

Abstract
In the paper, a three dimensional fracture propagation model was first established, then the factors that affect the fracture vertical growth were analyzed by means of the fracturing design software from the model. It is shown that although many factors influence the fracture height growth, the most important one is the minimum in-situ stress contrast between payzone and bounding zones. The pump rate and rheologic parameters for fracturing fluid also affect the height propagation to some extent. By analyzing the three dimensional fracture propagation model, we found that it is the stress intensity factors on the tips of line crack that have a direct influence on the height growth. Consequently, even though it is not easy to increase the in-situ stress contrast, we can manage to change the vertical distribution of flowing pressure in the fracture by adding some buoyant and sedimentary material to pad fluid, forming two artificial barriers at the top and bottom of the fracture. The two barriers decrease the flowing pressure in the fracture located at bounding zones, which is equivalent to the increase in in-situ stress contrast. Up to now, 13 wells have been fractured by optimizing treatment parameters and adding barrier material. All the wells had a great increase in oil production, and the fracture height inferred from well temperature logging is close to the perforated interval.
P. 165