As I read through the various SPEPO papers, I find it interesting how few papers go into any significant detail on the geology. Dealing with the geology is the focal point of many, if not most, of our production activities.
The relevance of geology was highlighted in some musings on a totally unrelated subject. I was asked how I would start a research program on climate change. After thinking about it for a while, it seemed that there were two options. We could start building enormous global circulation models with whatever physics we understand and ad hoc parameterizations for things we cannot easily deal with, or we could study the geologic record to determine how climate has changed in the past as guidance for what was likely to occur in the future. In the geologic record, I would include sediment and ice cores that have a wealth of information on temperature and atmospheric-gas compositions.
The geologic approach would allow us to gather information on historical sea level changes, temperatures, carbon dioxide levels, glaciations, and much more to help us understand how conditions are likely to change in our current interglacial warm period as a result of the usual forcing mechanisms. As I searched for information on these topics, I was impressed by the amount of work that has been done and the wealth of information on climate that is available from geological-based sources. You never hear about much of it, unfortunately, but the geology has a great story to tell.
In the same vein, I am continually surprised how often I find engineers who do not think that their reservoirs have natural fractures of any consequence—either no fractures, or the fractures that exist are inconsequential. I really think that they are ignoring the geology at their own peril, particularly if they are working in some of the more unconventional reservoirs. On the plus side, it is heartening to see the increased interaction and cooperation between SPE and various geology-oriented societies, such as the AAPG. I do think we need to figure out ways to increase the emphasis on geologic issues, both in education and in application.
This issue, as usual, has a wide variety of papers dealing with the full range of production activities. The first two involve workover operations with coiled tubing. In Workovers in Sour Environments: How Do We Avoid Coiled Tubing (CT) Failures, the authors present two case studies of coiled tubing failures during acidization of deep sour wells and give recommendations on methods to avoid such problems. Eliminating Multiple Interventions Using a Single Rig-Up Coiled-Tubing Solution presents a cost-benefit assessment of a coiled intervention approach using an internal plastic-coated electric-line cable for logging and perforating operations.
Multiphase flow in wellbores is the topic of the third paper. Modeling Nonisothermal Rapid Multiphase Flow in Wells Under Nonequilibrium Conditions is a numerical study of three phase flow with particular consideration of thermal effects and non-equilibrium gas separation from the liquid phases.
The next four papers deal with hydraulic fracturing. Awakening an Old Field—A Case Study of a Refracturing Program in the Greater Green River Basin is a study of refracturing of the second Frontier in the Fontenelle field area, with heavy emphasis on the use of the reciprocal productivity index method and diagnostic fracture injection tests. In Comparative Study of Flowback Analysis Using Polymer Concentrations and Fracturing-Fluid Tracer Methods: A Field Study, a laboratory study was used to evaluate the differences in flowback characteristics of chemical fracture tracers versus polymer concentration. Consideration for Future Stimulation Options is Vital in Deciding Horizontal Well Drilling and Completion Schemes for Production Optimization is a wide ranging discussion of issues associated with completing and fracturing horizontal wells. A theoretical study of fracture growth across layered interfaces is given in Effect of Formation Modulus Contrast on Hydraulic Fracture Height Containment, and the results suggest that any change in modulus across layers will hinder fracture height growth.
The next two papers deal with acidizing. High Viscosity Yield Acid Systems for High-Temperature Stimulation presents the development of a hydrochloric/formic acid blend that can be cross linked in situ for improved diversion. In Fracture Acidizing: What Role Does Formation Softening Play in Production Response, a laboratory study was performed to examine the strength reduction of limestone and dolomite that occurs because of exposure to various acid systems.
Oilfield chemistry in various forms is the topic of the following three papers. Low Sulfate Seawater Injection for Barium Sulfate Scale Control: A Life-of-Field Solution to a Complex Challengediscusses operational and chemical issues associated with the use of likely water sources in pressure maintenance and waterflooding operations, particularly targeted to offshore applications. In Formation Damage Through Asphaltene Precipitation Resulting From CO2 Gas Injection in Iranian Carbonate Reservoirs, the authors perform a coreflood study and compare it with modeling work to examine the asphaltene precipitation and associated permeability reduction. Inhibitor Performance on Corrosion and Erosion/Corrosion Under Turbulent Flow With Sand and CO2—An AC Impedance Study is a study of the effect of high fluid shear stresses and multiphase flow with sand on inhibitor efficiency and corrosion mechanisms.
The next three papers deal with the reservoir and its link with the wellbore. Quantification of Uncertainties for Drilling-Induced Formation Damage takes a statistical response-surface-modeling approach for applying near-wellbore flow models to formation damage problems. In The Relative Importance of Wellbore Pressure Drop and Formation Damage in Horizontal Wells, the authors use steady-state inflow and pipe flow equations to evaluate the relative flow restriction caused by these two mechanisms. A Rigorous Composite-Inflow Performance Relationship Model for Multilateral Wells considers lateral inflow performance, wellbore production, reservoir-wellbore crossflow, and wellbore hydraulics to predict deliverability of multilateral wells.
From a very broad operational perspective, Field Development Case Study: Production Optimization Using Continuous Multidisciplinary Reservoir and Production Monitoring discusses a field-wide optimization program for the giant Priobskoye reservoir in Russia employing 3D seismic, fracturing, waterflooding, artificial lift, reservoir modeling, and reservoir monitoring technologies.
Artifial lift is the topic of the next two papers. These include Analysis of Possible Applications of Dual ESPs—A Reservoir Engineering Perspective, which is a study of the benefits of using dual ESPs for production from multiple zones, water coning mitigation, deep sea wells, and other situations, and On Instability in Gas-Lift Wells and Schemes for Stabilization by Automatic Control, an evaluation of gas-lift optimization using various control structures to minimize casing-heading instabilities.
The final two papers in this issue deal with field-wide operational concerns. Well-Integrity Operations at Prudhoe Bay, Alaska is an outline of a well integrity management system and program that deals with tubulars, wellheads, operating procedures, well intervention, and personal accountability and responsibility. In Performance Appraisals of Gas/Oil-Separation Plants, the authors examined emulsion characteristics, separator operating characteristics, online analyzers and sensors, and other factors in an attempt to improve performance of these plants.
I would like to thank the authors, reviewers, and editors for this extra-large journal edition.