To drill a well, you need a rig, a crew, pipe, bits, mud and cement. But if you're planning to do some well construction, you also need a computer and some software.

One of the most important factors to consider when planning a well is the stability of the borehole, said a distinguished lecturer for the Society of Petroleum Engineers.

"Borehole instability during drilling can take many familiar forms, such as stuck pipe, hole squeezing, lost circulation, severely enlarged hole or difficult directional control," said Pat McLellan, president of Advanced Geotechnology. "Many related problems can arise when such wells are finally drilled to target, including uncertain formation evaluation, poor cementing, casing deformation and ineffective perforating. These issues cost the industry several billions of dollars a year around the globe in downtime, well construction costs and lost production."

One of the software programs to model wellbore integrity during the well planning phase is the new version of StabView, which also assesses the possibilities for lost circulation, fracturing and sand production. The software comes in two versions: StabView Express for single-zone analysis for a quick look, and the comprehensive, multizone version with advanced analysis and well design capabilities. The software uses efficient, rapidly converging algorithms to solve the fundamental equations that govern the behavior of the near-wellbore region. Some of the newest features include 3-D visualization, mud-shale chemical interaction effects, permafrost drilling, liner loading predictions and importing and exporting for interactive wellbore hydraulics modeling.

One of its most popular applications is designing underbalanced drilling operations in weak or fractured formations. StabView can be used to decide whether sand control is needed or if casing damage will occur during subsequent steam- or water-injection operations.

StabView was developed during a 6-year period incorporating cutting-edge research findings from several universities, research and development institutes and major oil companies. Funding was provided by two joint-industry projects supported by nine major operators, service companies and research institutes, including ChevronTexaco, Shell, Petrobras, Nexen, Weatherford and Baker Hughes.
"The joint-industry project model is an attractive way for many companies to accelerate the pace of research and development, but at an affordable price, and with a sharing of the risk involved," McLellan said.

Further information can be found at www.advgeotech.com.

Probabilistic well planning

While probabilistic estimation techniques routinely are used to characterize variation associated with geological and reservoir uncertainty, these techniques have not been widely applied to well construction activities. Instead, the traditional deterministic approach has provided inaccurate results that fail to address uncertainties in schedules and budgets, the level of exposure associated with those uncertainties and the individual risks involved in them. Risk-weighted probabilistic estimating considers the potential well operations (including sidetracking and equipment failure), and each event or task is allocated a probability or risk of occurrence with a time-based or rate-based distribution and cost schedule. Then this model can be run through a Monte Carlo simulation to find the associated probabilities of occurrence for all of the possible outcomes. With this information, the operator will know the chances (10% chance = P10, 50% chance = P50) of achieving a project within any given time and cost number. Based on the level of risk the company is willing to take, managers can make more informed choices on operational and budgetary commitments.

The Peak Group in Aberdeen, Scotland, recently upgraded its probabilistic well planning software program P1. The original application was launched 2 years ago. It used Monte Carlo probabilistic simulation techniques to deliver a realistic representation of the spread of possible time and cost outcomes from well construction activities. Since then, Peak has gathered a vast amount of real feedback from users, and significant improvements were made with the release of Version 2.

The new version's central Cost Library allows users to maintain and access costs on all projects. Additional cost types and multiple currencies can be used within a single project, with the user defining exchange rate distributions of possible values expected. Contingencies can be applied to selected phases of the project rather than over the entire model. Version 2 allows particular phases to be disabled for simulations as well as the copying and pasting of phases and activities within and between models.
Also incorporated is the ability to prepopulate such recurring variables as tripping speeds for tubulars, and depths can be entered as true vertical or measured depths. Users can insert multiple activities from the Activity Library, and directional data can be imported from text and ASCII file formats.

A "wizard" feature helps new users step through each of the main input screens in sequence.
Finally, the software features additional flexibility to change units within models from feet to meters and define transit time to site for day rate cost items.

Peak Group Managing Director Andrew Paterson said, "Top operators are now escaping the limitations of deterministic planning, replacing this with the performance-enhancing probabilistic approach. This enables significantly improved understanding of time, cost and technical exposures. This, in turn, facilitates more informed decision-making, timely activity execution and more efficient utilization of resources. The technique also adds huge value to the concept and technology selection processes. We are finding that in many cases use of P1 has empowered decision-makers to opt for technologies and concepts which simple deterministic planning and intuition would not have pointed them to."

A principal benefit of using P1 is the improved understanding of timing and costs through risk identification and mitigation at the project and task levels. The process allows operators to test technical and operational options and identify and focus on areas of high impact. The program also can be used to weigh the risk of a project against the general level of risk in an organization's operations as a whole. The output of a risk model offers a sound basis for negotiating commitments between customers and suppliers or between business managers and project managers. Time and cost distributions allow asset groups and partners to have a far greater understanding of risks and commercial exposure prior to project or well sanction.

Planning directional wells

Back in the old days, drillers didn't need software to plan or drill a well. However, with the advent of horizontal and directional wells and more complicated well trajectories to tap multiple or difficult targets identified using 3-D seismic, well planning software becomes critical. Several software packages focus on drilling directional wells.

WinServe, from Houston, Texas-based Performance Drilling Technology, provides the traditional survey calculation routines with complete 3-D well planning capability and 2-D display onscreen. Special features are the graphically driven, 3-D vectored well-profiling capability, a Ouija board calculator and exported DXF files to any CAD program to generate wall-size plots. Three versions are available: the full WinServe well planning package, WinServe Lite for directional drillers and WinServe SV for measurement-while-drilling and survey companies.

Paradigm Geophysical's Sysdrill Director has a unique well-planning spreadsheet that allows construction of vertical, directional or horizontal wells using predefined well profiles to multiple geometric targets. Planned casings, hole sections and comments can be entered along with planned tool errors to compute the expected positional uncertainty. Using a similar spreadsheet, the measured survey can be entered manually or imported from disk. Multiple survey logs can be stored and used to create the definitive view of the well. A third spreadsheet allows the user to project ahead to the driller's target or return to plan. Actual vs. planned graphical views can be launched at the click of a button. Anti-collision scans can be performed online from the well planning, survey or project-ahead spreadsheets.

3D3 Planner, from Houston-based Technical Toolboxes, is a comprehensive suite for well planning, design, trajectory optimization, surveying and reporting. It can be used for directional drilling of wells and underground pipelines. The spreadsheet system enables the use of what-if scenarios to speed up the planning process. Predefined 2-D or 3-D profiles can be combined to build complex geometries. Two planning methods, Double Circle and Spline in Tension, are available, and a third method, Build & Turn, will be available free to registered users in the next software release. The well path optimizer integrates with the company's torque-and-drag module to determine the ideal combination of trajectory design parameters. The survey calculation module uses three trajectory models: minimum curvature, radius of curvature and average angles. Planned path surveys include dogleg and toolface, used by the field engineers to orient the directional drilling equipment correctly.

PathTracker 5.0, from Onscreen Software Solutions of Calgary, Alberta, is a directional and horizontal drilling, survey calculation and well planning program for PCs. "Our DOS programs are likely the most pirated software in the directional drilling industry today," said sales distributor Phil Gilkes. This program is the Windows version of that same package, only with a 3-D PathPlanner. The package is available for a 10-day trial download. "If you're not convinced that PathTracker and PathPlanner are the easiest-to-use directional tools on the market, just let the trial license expire, and the program will revert to demonstration mode," Gilkes said.