Exceptional concepts go the distance

Oil and gas operators have always sought the best price-to-performance ratio—the lowest completion cost for the highest-producing wells. In a perfect world, a completion system would be inexpensive and operationally efficient, yet effective for every reservoir. Sometimes it’s the combination of existing ideas that results in something not only innovative but incredibly valuable.

This was the case for the combination of horizontal drilling with multi-stage hydraulic fracturing systems. In the past, these technologies operated in separate spheres. The combination was an inspired pairing that unlocked our current unconventional industry.

At the periphery of the industry is another inventive pairing that evolved from horizontal multi-stage completions. The integration of HPHT/offshore capabilities with multi-laterals has the potential to increase efficiency and create value for operators.

A multi-lateral development can be an ideal strategy for high-cost drilling markets, such as offshore.

MULTI-LATERAL COMPLETIONS

A multi-lateral is a well with two or more laterals drilled from a main motherbore, Fig. 1. The strategy can lower costs while enhancing production by accessing multiple pay zones at different depths. The situations where multi-lateral completions are suitable include:

•   Complex geology, where drilling more wells is not economical
•   High-cost drilling markets (such as offshore) 
•   Plays, where increased reservoir exposure is required (such as heavy oil) 
•   Areas where geological targets are segregated
  

To achieve these benefits, the technical goals of multi-laterals usually include:

•   Junction/isolation integrity
•   Lateral re-entry.
  

Fig. 1. By drilling and completing two or more laterals from a main motherbore, multilateral wells can lower costs while enhancing production by accessing multiple pay zones at different depths.

Multi-lateral systems have been available for years, but many operators consider them to be niche technology that requires expensive equipment and experts. Although complex and expensive multi-lateral solutions do exist, they don’t have to be that way. Over the years, service companies have begun introducing simpler junctions.¹

Starting in 2006, Packers Plus developed and patented a simplified process that has led to an extensive run history of over 1,000 multi-lateral completions (Table 1). These have been implemented by operators throughout Western Canada’s Bakken, Cardium and Montney formations.

High oil prices had allowed operators to profitably drill a large number of wells, to maintain and/or increase production to offset rapidly declining rates. However, after years of depressed oil prices, operators may no longer be able to afford such inefficient strategies.

The buy-in is growing steadily. Several operators in the Permian basin have announced production increases attributed to multi-lateral completion designs, with a continued focus on advancing with the technology.² A Norwegian operator also recently completed the first-ever dual-lateral in the Kurdistan region of Iraq.³ As with the trend of horizontal multi-stage completions over the last decade, a track record showing the reliability of multi-laterals will encourage wider adoption.

INTERVENTIONLESS SLEEVE COMPLETION TECHNOLOGY

Sliding sleeve systems are known for their efficiency and minimal non-productive time, because the entire wellbore can be stimulated in one continuous pumping operation. Using packers for isolation, balls are pumped from surface to land in their matching sleeves. Increasing hydraulic pressure shifts the sleeve open for stimulation, simultaneously closing off the lower section.

It would be fair to say that this was disruptive to the industry. Previously, hydraulic fracturing relied on conveying tools on wireline or coiled tubing for each stage. Although these methods are still mainstream, they are inherently time-consuming.

Interventionless sleeve completion technology gave operators the ability to economically drill and stimulate extended-reach horizontals in unconventional reservoirs, and provided a springboard for a whole new class of completion solutions. Sliding sleeves were initially designed as a single-point entry treatment for open-hole wells. Since then, however, the concept has been a springboard for a wide range of innovation.

Innovation journey. Here is a rundown of Packers Plus' evolution to multi-lateral and HPHT completion technology:

•   Increase in stage capability by changing ¼-in. seat increments to 1/8-in., then to 1/16-in., using improved materials
•   StackFRAC HD-X further boosted stage capability, featuring seat increments tighter than 1/16-in.
•   StackFRAC HD installed in hundreds of multi-lateral wells in North America 
•   Titanium XV introduced as a heavy duty version of StackFRAC HD, rated to 15,000 psi and higher, for HPHT environments, Fig. 2. 

•   Inferno further built on Titanium XV’s HPHT capabilities for ultra-high-temperature geothermal applications.

Since 2011, Titanium XV has been installed in over 275 wells and treated over 5,500 stages around the world, Table 2.

Packers Plus also has been involved in offshore completions since 2006, in locations in Brazil, Republic of the Congo, Gabon, Romania, Vietnam and the United Kingdom, Fig. 3.

Fig. 2. The Titanium XV system is rated to 15,000 psi for high pressure / high temperature environments. Since 2011, Titanium XV has been installed in over 275 wells around the world.

Fig. 3. Packers Plus has been involved in offshore completions since 2006, in locations such as Brazil, Republic of the Congo, Gabon, Romania, Vietnam and the United Kingdom.

WINNING COMBINATION: WORLD’S FIRST OFFSHORE, ACID-STIMULATED MULTI-LATERAL WITH MULTI-STAGE COMPLETION

It’s not surprising that the world’s most advanced multi-lateral systems have typically been used offshore.⁴ These are among the most technically challenging projects, but also the most potentially lucrative. Naturally, only the most proven technology is selected for these high-stakes completions.

An operator in the United Kingdom, focused on oil and gas operations in the North Sea, was seeking a low-cost completion solution for its offshore development. With multiple target reservoirs in the same area, the operator required a solution to maximize stimulation effectiveness and minimize cost.

Fig. 4. A 14-stage StackFRAC HD system was installed in each leg for multi-stage acid treatment.

Design considerations. To provide the most cost-effective technology solution for the project, the Packers Plus team designed for simplicity. Using a TAML Level 2 multi-lateral junction (Fig. 4), and proposing the same straightforward and proven StackFRAC HD design for each leg, the completion would be able to access two separate reservoirs from a single wellbore.

The dual-lateral project was designed with two identical 5.5-in. 14-stage StackFRAC HD systems, including key considerations, such as:

•   Reservoir characteristics and stress profile through the laterals
•   Choice of fluid, volumes and timing to maximize fracture propagation and area, and optimize wellbore conductivity
•   Efficiency of using a full boat of acid per lateral, as a large treatment would also minimize non-productive time. 

Mitigating risks was also a major part of planning. A wealth of experience was available from recent nearby offshore projects, as well as from the extensive StackFRAC HD run history. From these lessons learned, the following decisions were arranged to reduce operational risk:

•   Using degradable balls to avoid mill-out operations
•   Contingency planning: 
•   Planning the second leg to be drilled far enough from the first to avoid inter-wellbore communication.

Results. The two laterals were drilled, completed and stimulated within three months. Outside of drilling, installation-to-stimulation operations for both legs were completed within a total of 12 non-consecutive days, Fig. 5. 

Leg 1 was drilled, and the 14-stage StackFRAC HD system was completed in four days. To minimize non-productive time, the well was stimulated immediately after reaching setting depth. The 14 stages of acid treatments were completed in three days. 

Once operations were complete for the motherbore, a whipstock packer was set, and the second leg was drilled. Leg 2 was completed in only two days using the same setup and system as the motherbore, and later stimulated over two more days. 

The success of the on-time and on-budget project is attributed to a strategy emphasizing simplicity, efficiency, and the anticipation and mitigation of operational risks.

Besides introducing the operator to operational and economic efficiencies, the well has already shown higher-than-expected initial production.

CONCLUSION

As with the combination of horizontal drilling and multi-stage hydraulic fracturing systems that began the unconventional revolution, the integration of HPHT/offshore-capable technology with multi-lateral completions will generate new interest for a variety of challenging environments around the world, including offshore reservoirs. 

As shown by the success of the implementation of StackFRAC HD in a North Sea dual lateral, the industry is stepping toward the reality of lower-risk, economic, high-efficiency multi-lateral completions. 

References

¹ Langley, D., “Multilateral completions on rise but still a niche,” Drilling Contractor, July/August 2011.

² Walzel, B., “Unconventionals lead American oil resurgence,” E&P, April 2018; Addison, V., “Eyeing growth: Occidental looks to increase Permian production, E&P, February 2018

³ GlobeNewswire; “DNO ramping up Kurdistan investments; reports strong 2017 results,” DNO ASA, February 2018.

⁴ Deluca, M., “Multilateral completions on the verge of mainstream,” April 1, 1997.