Progress in Horizontal Technology Yields Incremental Bonuses

Nearly 110 participants in an SPE Applied Technology Workshop (ATW) on Horizontal Wells heard Pemex Subdirector of Technical Coordination Heber Cinco Lay and Canadian Triton Intl. President and ATW Chairperson Jack Nelson explain synergistic developments that have contributed to elevating horizontal drilling to a qualified, viable alternative to vertical wells. Held in Tabasco, Mexico, the 2-day ATW stressed the importance of lateral-drilling technology to Pemex operations and invited knowledge exchange.

Referencing the industry’s steep learning curve with multilateral drilling, Nelson traced the progression of lateral-well technology from the first recorded true horizontal well drilled near Texon, Texas, in 1929 to the Austin chalk and Bakken shale successes during the 1980s to horizontal displacements running to more than 23,000 ft in the Dan field. The technical program, consisting of eight sessions, featured 25 speakers from major operators and service companies presenting on the following topics:

Why and When To Plan To Drill Horizontal—Included a case history on the Agua Fria field, increasing productivity using lateral-well technology, application-risk-evaluation barriers and limitations, and an update on specific horizontal-well technology.
Geomechanics and Advanced Wellbore Modeling—Included horizontal-wellbore stability issues; effect of anisotropy on productivity ratio for high-permeability, naturally fractured reservoirs; and workflow based on an integrated Earth model.
Horizontal Drilling Techniques—Included wellbore quality and effect on drilling and completion, underbalanced lateral drilling, and well construction.
Horizontal Completion Techniques—Included the candidate selection process for horizontal, openhole completions; openhole horizontal-well sand-control completion options; and practical installation of an expandable sand-control screen.
Well Intervention Issues and Remedial Operations—Included the importance of geomechanical parameters in horizontal drilling, wellbore-debris-management systems, and use of swell packers for zonal isolation in long deviated horizontal and multilateral open holes.
Evaluation of Horizontal-Well Performance—Included a case history of Chevron’s Captain field (an offshore heavy-oil horizontal-well development project) and stimulation of horizontal wells in low-permeability, deepwater, carbonate reservoirs.
Workflow Process: Keys to Success—Included discussion of Pemex’s “front-end loading” modeling and design methodology, the impact of digital technologies on planning and drilling horizontal wells, and motivations for drilling horizontal and multilateral wells in the Faja Petrolifera del Orinoco in Venezuela.
New Technologies and New Challenges—Included technological advances in horizontal gravel-pack systems, use of horizontals for heavy oil in deep water, and a case history of an expandable screen applied to a horizontal gas well in Mexico.

Laterals: Why and When

Pemex Well Completions Manager Fernando Flores, Halliburton Senior Technical Adviser Eduardo Pacheco, Schlumberger Senior Well Engineer Donald Straub, and Schlumberger Drilling Engineer James Roxo kicked off the workshop with practical information on factors that impact horizontal productivity, including well path, rock mechanics, anisotropy, formation damage and skin effect, completion, and recent improvement methods. Insights into the application of horizontal-well technology in Mexico’s Agua Fria field, where multilateral wells are being considered for future development, were shared:

Horizontal wells without hydraulic fractures achieve the same production as vertical fractured wells, but better performance is expected from hydraulically fractured horizontal wells.
3D seismic is beneficial in locating sand bodies for horizontal drilling.
Highly deviated wells are preferred in such sandy structures.

It was emphasized that sufficient planning of horizontal drilling is required for success; it is important to recognize that lateral technology is only another completion option and should be compared with all other options. Critical success factors to consider include directional well planning, drillstring design, torque and drag, drilling fluids, hole cleaning, drilling optimization, well placement, surveying, wellbore stability, and casing running and wear.

Geomechanics Advanced Modeling as Precaution

Geomechanics Intl. Director–North America Chris Ward, Schlum-berger Reservoir Engineer Rodolfo Carvajal, and Schlumberger Scientific Adviser Tom Bratton communicated how geomechanics and advanced modeling techniques are used to address issues of wellbore stability, effects of matrix/fracture interaction, and performing a data audit. Because wellbore instability is one of the biggest contributors to nonproductive drilling time in horizontal wells, instruction provided in the session “What To Look Out for on the Rig” was of particular interest to workshop participants. Following a discussion on how geomechanical models are built—using stress diagrams, a world stress map, and sources of geomechanical data—participants were shown how rock-mechanical properties are derived from log data. Also shown was how logs are used to verify and calibrate a geomechanical model and to predict wellbore stability.

Numerical simulation models can help describe the effects of matrix/fracture interaction in naturally fractured reservoirs developed using horizontal drilling. A comparison of productivity ratio for vertical and horizontal wells was shown along with comparative results and available analytical studies. Results of case-study data were input to a black-oil simulator with different values of kv/kh, different matrix/fracture interactions, and different permeabilities. These results showed that dual-porosity parameters have no relevant effect on flow-rate profiles or productivity ratio; the effect of anisotropy on flow-rate profiles is less important in high-permeability cases than in low-/middle-permeability scenarios.

Also during this session, a data audit was performed for compiling a database for seismic, geology, drilling, and logging for use in completion and production. Wellbore-instability mechanisms were discussed, in particular mud-density control and the importance of hole cleaning. Managed-pressure drilling was presented as a solution to rock failure.

Drilling Laterals

The topics of wellbore and well-construction quality were highlighted in presentations by Halliburton Senior Technical Adviser David Chen, Jack Nelson, and Pemex Petroleum Engineer Jaime Ortiz. Poor hole quality is a fundamental drilling problem that has profound impacts on both drilling and completion operations. One presentation addressed hole spiraling, including the difficulty in spotting spiraling using survey data and some solutions to the problem. Challenges associated with spiral holes are reduced wellbore pass-through area; higher friction forces, poor sliding rate of penetration (ROP), and reduced weight transfer; poor log response; poor cleaning, cuttings-bed traps, backreaming, and short trips; stuck pipe; poor cement jobs; and unstable bits, short bit life, higher vibrations, and more tool failures.

Discussion regarding underbalanced drilling (UBD) techniques as applied to horizontal wells covered these common motivations for implementing a UBD operation:

Reduce invasive formation damage and near-wellbore skin effects to obtain higher production rates and reduce or eliminate costly completion/stimulation operations.
Significantly increase ROP to reduce drilling time and costs and reduce problems such as lost circulation, high torque and drag, and differential sticking.
Flow-test while drilling.
Flush reservoir fluids while drilling

Commentary also focused on the UBD method as being economical in depleted, low-pressure reservoirs and identifying productive zones during drilling. Time was spent comparing the use of designer drill-in fluids with UBD methodology, reviewing the pros and cons of zero formation damage, and establishing the relationship of fluid mechanisms and borehole stability using UB methods.

The final part of this session featured analysis of an economic model of the Chicontepec area. Through the exercise of obtaining a clear definition of horizontal wells, their applications, and completion types, the group concluded that horizontal methodology is an expensive and multidisciplinary activity to be analyzed carefully before being undertaken. To successfully drill horizontally, it is necessary to form multidisciplinary groups and use a critical-path method to coordinate and control the quality of the project.

Examining Completion Options

Beginning with a look at the horizontal-candidate selection process for open hole followed by a discussion of the options for openhole completions with sand control, workshop attendees also received practical information on installing an expandable sand-control screen. Chevron Senior Adviser Rick Dickerson, Well Completion Technology President Bill Ott, and Chevron Technical Adviser David Underdown offer these insights:

Key drivers in candidate selection—sanding tendency, kv/kh, uniformity and sorting coefficients, well life and expected production rate, water- and gas-shutoff requirements, and presence of reactive shales.
Advantages and disadvantages of using standalone screens, an openhole gravel pack, expandable screens, and formation-isolation valves.
Unwritten practices for installing expandable sand-control screens.

Intervention/Remedial Operations

This session entertained issues related to these topics: Importance of Geomechanical Parameters in Horizontal Drilling, Wellbore-Debris-Management Systems, and Swell Packers. Inst. Mexicano del Petróleo Petroleum Engineer Joaquin Mendiola addressed the use of geomechanics to reduce the risk of wellbore instability, putting emphasis on coring, hole and/or casing collapse, and optimal bit selection. Baker Oil Tools Senior Engineering Manager Jim McNicol presented a holistic approach to manage debris, using new technology to optimize well cleaning. Easy-Well Solutions Regional Sales Manager Oscar Barrios demonstrated application of the swell packer as an enabler to various completion techniques, including horizontal, multilaterals, smart wells, expandable sand screens, and standalone screens.

Evaluating Performance

For horizontal completions, proof is in the application. Chevron Research Consultant–Well Performance Bill Huang and Petrobras Petroleum Engineer Carlos Pedroso reported results from the Captain field and in the Campos basin, respectively. These conclusions were reached:

Horizontal technology can be applied successfully in offshore heavy-oil projects.
Sand-control design evolution from prepacked screen to openhole gravel pack offers a good example of the continuous improvement process.
Horizontal gravel packs can be placed over extended intervals effectively.
Gravel packing improves zonal isolation.

Also, the effects from stimulations in horizontal wells in Campos basin fields were presented and interpreted.

Workflow: Critical to Success

Pemex Petroleum Engineer Benito Ortiz, Jack Nelson, and Drilling Consultant Henry Melendez and Reservoir Consultant Oswaldo Hidalgo, both of Copy R.C.A., brought the importance of workflow to the attention of workshop attendees. Ortiz traced a “front-end loading” methodology being applied by Pemex on five assets. Nelson commented on the benefits of the new digital workflows, described how they increase the bottom line, and identified technical hurdles that currently impede implementation. Melendez and Hidalgo recounted the maturity of horizontal and multilateral drilling technology that allows it to be used in exploitation of heavy- and extra-heavy-oil reservoirs in Venezuela.

New Technologies, New Challenges

Speakers in the final session were BJ Services Product Line Manager David Walker, Petrobras Production Engineer Luis Bianco, and Baker Oil Tools Senior Applications Adviser Carl Stockmeyer, who addressed the future of horizontal technology. Walker detailed future tool development for a single-trip horizontal-washdown frac-/gravel-pack system with inflow-control valves and integrated data collection. Bianco spoke about productivity for heavy oil in deep water—well-testing issues; completions for maximum productivity; and well geometry as related to drainage area, fluid testing, and multizone, multilateral fishbone frac-pack completions. Stockmeyer shared details of the Arquimia field expandable-screen installation and pointed out the benefits of such screens in horizontal wells, including providing formation support, maximizing internal diameter, stopping fines migration, eliminating axial flow, and stopping corrosion.