Back to the Future
The history of "scientific" oil-well drilling has its beginnings atthe end of World War II. The first wave of scientific drilling was an era ofslide rules and hand calculations. The technology of this era consisted ofrelatively simple, but effective, models of very complex phenomena. ClaudeHocott once told your editor that any calculation that could not be summarizedon a note card would not be useful, and for that era, he was correct. Today, itis hard to appreciate the tedium of evaluating these simple formulas with sliderule, tables of logs, and pencil and paper.
The next wave of scientific drilling introduced a new computational tool,the electronic computer, beginning in the 1970s. Young engineers, who had usedprimitive computers as part of their university education, were now ready tobreak Hocott’s one-card rule and delve into the complexity of the phenomena ofdrilling.
Your editor speculates that we are beginning a third wave of scientificdrilling. The days of novel computer application are reaching their twilightyears, and a period of evaluation and consolidation is beginning. Computerscience and numerical analysis are at a much higher level of accuracy andsophistication today than they were in the 1970s era, and many of thetechnology developments of that era should be re-examined in the light ofmodern techniques.
In this issue, there are four completion topics and nine drilling topics.The completion papers consist of the following papers: A New Skin-FactorModel for Perforated Horizontal Wells answers the question: "What isthe best way to perforate horizontal wells with anisotropic permeability?"The results show that the azimuth of the perforation is the key. If theperforations are normal to the maximum permeability direction, perforationswill enhance horizontal well flow compared to an open hole completion.Geomechanics Aspects of Multiple Fracturing of Horizontal and VerticalWells. Although fundamentally similar to fracturing vertical wells,fracturing horizontal wells have unique aspects that require special attentionfor successful treatment. Because fracture orientation depends on welldirection relative to the formation stresses, successful fractures depend onthe well completion and its orientation, which is further complicated by thepresence of multiple fractures. An Alternative to Sand-Control Screens: IsPermeable Cement a Viable Option? First, the bad news: for a variety ofreasons detailed in this paper, permeable cement does not yet appear to be aviable option as an alternate sand-control method for primary openholecompletions. However, the system presented in this paper may find use inremedial sand-control situations. For instance, squeezing perforations withpermeable cement could ensure sand-free production over a limited time whilemaintaining full wellbore access. Design and Implementation ofRetention/Filtration Media for Sand Control. The factors that control theperformance of sand-control screens that use different metal mesh weaves is notgenerally well understood. This paper provides techniques to design andengineer a premium sand-control screen with retention/filtration for thespecific particle size distribution of the formation, maximizing oil productionwhile minimizing solids production.
The drilling papers include: Remote Real-Time Well Monitoring and ModelUpdating Help Optimize Drilling Performance and Reduce Casing Strings.Feedback and updating the pre-drill velocity-to-pore pressure with realmeasured data enabled accurate pore pressure prediction in a GoM well. Themonitoring of true formation pressure thus allowed drilling to proceed withinthe constraints of a very tight mud envelope, resulting in a deeper casing seatand elimination of an entire casing section. State-of-the-Art in CoalbedMethane Drilling Fluids. For horizontal coalbed methane wells, theimportance of the drilling fluid is magnified because the fluid must stabilizethe wellbore during drilling but minimize damage to production. In this paper,the fluid is designed to match surface chemistry of the coal, and provide botha matting system to provide borehole stability and a breaker method to removethe matting once drilling is completed. Transport of Small Cuttings inExtended-Reach Drilling. Field experience has shown that inefficienttransport of small cuttings is a main factor for excessive drag and torqueduring extended reach drilling. Drillpipe rotation combined with polymericdrilling fluids was found to efficiently transport small cuttings duringextended reach or horizontal drilling. Hole Cleaning During UBD inHorizontal and Inclined Wellbore. This paper presents a new mechanisticmodel for cuttings transport, developed by combining two-phase hydraulicequations, turbulent boundary layer theory, and particle transport mechanisms.It is shown that the model is useful for predicting minimum annular velocityand cuttings bed thickness in horizontal and inclined wellbore geometry.Kikeh Batch Setting: Case Study. The semisubmersible rig Ocean Rover wasused by Murphy Sabah Oil Company to batch-set 23 wellheads in 4,350-ft-deepwater with zero health, safety, and environment (HSE) incidents. Implementinglessons learned and development of recommended practices resulted in continuousimprovement throughout the project. Improving Formation-Strength Tests andTheir Interpretation. Crucial decisions on mud weight, kick tolerance, andthe setting depth of the next casing string are based on the outcome offormation-strength tests such as leakoff tests or formation-integrity tests. Inthis paper, the authors highlight several of the problems underlying currentformation strength tests and their interpretations, illustrating them withactual field examples, and they show how test artifacts can be either avoidedor accounted for. Design of Well Barriers to Combat Circulation Losses.This paper presents a new mechanistic model for fracturing called "theelastoplastic-barrier model." It is different from other recent models, andit is verified with laboratory experiments. It defines optimal barrier filtrateloss to place particles in the loss zone, and the mechanical strength of theparticles required to resist losses. Tests demonstrated that boreholefracturing resistance could be improved significantly by changing mudcomposition. Shear-Type Borehole Wall Shifts Induced During LostCirculations. Previously, stuck pipe problems were assumed to be caused byborehole breakouts, differential sticking, and cutting pack offs. However,thorough examinations of borehole walls using borehole televiewers show thatsome stuck-pipe problems may also be caused by shear type borehole wall shifts.In this paper, a new fracture model for a borehole is developed using a3D-dual-boundary element method. This method allows different displacement andstress traction at the two fracture surfaces along a fracture plane around aborehole. A New Method of Producing Laterally Stable PDC Drill Bits. Bitwhirl is well documented as a major cause of damage topolycrystalline-diamond-compacts (PDC) drill bits, and result in short runs,low rate of penetration (ROP), high cost per foot, poor hole quality, anddownhole tool damage. Hence, consistent lateral stability is highly desirablein PDC bits. The paper presents a new method of producing PDC drill bits thatreduce or eliminate bit whirl. The new approach assumes that it is the responseof the bit to forced motion off its center that causes whirl.