Advanced multi-stage completion systems maximize efficiency

The price of oil experienced a recovery from fourth-quarter 2020 forward, amid the Covid pandemic, and in 2022, WTI eclipsed the $100/bbl mark for the first time since 2014. But with the price hovering around $80/bbl since November 2022, producers are reminded of the volatile nature of commodity prices and the need to continuously focus on reducing lift costs. 

For completion programs, that means reducing the costs of frac operations, while still delivering an effective treatment along the entire lateral of a horizontal well to maximize production potential. The common trends for all well designs are a move to: 

• Extended-reach laterals 
• Increased stage count 
• Tighter stage spacing. 

There are several completion methodologies being deployed across the Canadian market—as geology changes, so does the optimal stimulation technique. Frac rates range from 1-14 m3 per minute with varying sand concentrations and tonnages per meter. 

CEMENTED BALL DROP SYSTEMS 

Increasingly, we are seeing producers deploy cemented ball-drop completions for either the toe stages as part of a hybrid completion or the entire wellbore, Fig. 1. By moving away from plug-and-perf or coiled tubing sleeves, producers can complete fracs quicker, increase frac rates and reduce required post-frac operations, which will lower cost and improve production potential. Packers Plus has two options for cemented ball-drop sleeves, Fig. 2: 

• Diffusor sleeve – single-point entry stimulation (one port stimulated at a time) 
• QuickPORT IV sleeve – limited entry stimulation (multiple ports stimulated at a time).  

In addition, other key technologies that make up an effective extended-reach lateral completion strategy include:  

• Packers Plus Inner Armor erosion coating – ensures completion equipment integrity during high-rate/tonnage stimulation 
• SF903 dissolvable balls – eliminates the need to drill out post-frac 
• Toe-AP hydraulic sleeve – opens at a specific absolute pressure, saving time and cost in delivering an effective treatment of the first stage (testable toe option available) 
• Aerostat floatation subs (casing and drill pipe options available) 
• ePLUS Retina monitoring system (verifies all shift events). 

Fig. 1. Diffusor and QuickPORT cement ball drop technologies.

Fig. 2. Cemented drop ball capabilities with liner and seat sizes.

COMPLETION TRENDS 

The next section will explore new completion trends and highlight how cemented ball-drop technologies can help operators improve the effectiveness of their stimulation programs and maximize the production potential of every well. 

Extended-reach laterals. Over the last 10 years, the number of horizontal wells completed with lateral lengths exceeding 3,000 m, in unconventional plays across North America, has grown significantly. And longer laterals mean more stages. Single-digit stage counts from the early days of multi-stage stimulation at the turn of the century have given way to 50-stage jobs commonly being pumped, and wells with more than 100 stages are becoming more frequent.  

Generating enough weight-on-bit to mill out frac plugs post-stimulation or generating enough weight to shift coiled tubing sliding sleeves are two challenges that can arise when completing extended-reach laterals. Combining a hydraulically activated toe sub with sliding sleeve technology in the lower stages of an extended-reach lateral well can further enhance the operational efficiency experienced for the first stage.  

Ball-activated sleeves transformed well completions through continuous pumping operations. The benefits of reduced time and cost associated with continuous pumping operations in single-point entry ball-activated sliding sleeves were soon adapted to allow one ball to open multiple sleeves in a stage—mimicking the limited-entry treatment of plug-and-perf. These systems were soon developed further to work in cemented liner completions. 

Ball-activated sliding sleeves allow the operator to pump the frac continuously, eliminating down time and reducing fluid requirements when compared to plug-and-perf. To complement the reduced operational time during stimulation, SF903 dissolvable balls were developed to eliminate the need to drill-out post frac. 

 High-rate stimulations. The trend toward pumping stimulation treatments at higher rates, with high fluid volumes, higher proppant loads, tighter stage spacing, and higher stage counts, has contributed to better operational efficiency and higher production. However, the same proppant that improves production—especially at high volumes—can also erode downhole tools to the point of failure, resulting in expensive remedial solutions or lower production and potentially both. 

In plug-and-perf completions, proppant eroding and enlarging perforations cause the first cluster to accept most of the fluid, while others in the same interval receive minimal or no treatment. Production logging also has shown that only 20% to 50% of the intended fracturing targets in a perforation cluster were producing at fracture-stimulated rates. This inefficient use of proppant leads to lower-than-expected production and reduced return on investment. 

In ball-activated sliding sleeve systems, the turbulence of fluid flow through a seat causes a slight pressure increase. This is inconsequential for one seat, but a completion string of 40 to 50 sliding sleeves can add thousands of pounds of pressure in additional friction, which is a source of operational concern. Fortunately, these issues have been mitigated specifically for both single-point and limited-entry completions by reducing fluid friction, and mitigating ball/seat and entry point erosion. 

Packers Plus sliding sleeves were re-engineered to mitigate cumulative fluid friction. Using computational fluid dynamics simulation, the reshaping of the internal fluid path reduced pressure drop (and thus fluid friction) by over 60%. These design enhancements to the Diffusor Sleeves and QuickPORT IV Sleeves, combined with Packers Plus Inner Armor erosion coating, ensures completion equipment integrity during high-rate/tonnage stimulation.  

The diffusor sleeves also incorporate Packers Plus’ StackFRAC HD-X ball seats. These ball seats come in increments as low as 1/64-in., which enable the delivery of high intensity stimulation treatments with rates as high as 16 m3/min and 200 tonnes of sand per stage. A high rate can even be achieved at the toes of the wells, where the smallest seat size is typically no smaller than 2-in. 

The nozzles on the QuickPORT IV sleeves are reinforced with tungsten carbide, which virtually eliminates erosion of the entry point during stimulation, while the offset spacing of the nozzles facilitates even distribution of the treatment across the entry points. 

QUICKPORT IV OVERVIEW 

The QuickPORT IV sleeve is a ball-actuated, hydraulically activated injection/production port used with the Packers Plus limited entry system. The sleeve allows for more than one stage to be activated with the same size actuation ball for limited entry stimulation. There is a variety of ball sizes available, allowing for multiple stimulation treatments to be run in sequence. 

The QuickPORT IV sleeve flow ports are available in a variety of sizes to optimize the limited entry stimulation treatment. After stimulation, the well can be immediately put on production and if desired, the ball seats can be milled out, based on the operator’s completion requirements, Fig. 3.  

Fig. 3. Schematic and feature callouts of QuickPORT IV.

The QuickPORT IV sleeve is assembled in the completion tool string, according to well requirements and run into the wellbore to the planned depth. The appropriate ball size is inserted into the string and pumped down to the uppermost sleeve in the limited entry treatment zone. The tool string is then pressured up, and the sleeve is shifted open. The ball then passes through the sleeve and continues down the liner to activate other QuickPORT IV sleeves within the treatment zone. 

Once the QuickPORT IV sleeves are opened, the designed stimulation rate can be achieved. Each subsequent zone is treated, using an incrementally larger ball to activate the sleeves. The larger ball size also isolates lower zones from the up-hole pumping operations. After stimulation, the ball seat can be milled out, if desired. 

CASE STUDIES 

Diffusor sleeves in a full wellbore. An operator in central Alberta planned to complete three wells with high-rate slickwater stimulations. The wells were not on a pad, so the efficiencies of plug-and-perf operations were not an option. The liners were deployed on drill pipe and cemented in place below a Packers Plus PrimeSET liner hanger. Stage 1 was stimulated through the Packers Plus Toe AP hydraulic port, and the remainder of the stages were stimulated with diffusor sleeves (35,38 and 55 stages), Fig. 4. 

Fig. 4. Cemented drop ball diffusor.

Balls were launched at full frac rate and 10 m3 per minute was maintained until 5 m3 prior to landing the ball, when the rate was slowed to 2 m3 per minute until the port had shifted. Acid pumped immediately behind the ball helped with formation breakdown, and the operator was able to increase rate quickly and begin the frac. This procedure reduces fluid volume requirements and increases the speed of operation. Frac parameters were as follow: 

• 10 m3 per minute frac rate (all stages) 
• 30 tonnes of sand/stage 
• Slick water with 12% N2 

In this case, all stages were stimulated successfully, and wells were put on production.  

Diffusor sleeves overcome deformation issues. An operator experienced casing deformation challenges during both coil frac sleeve and plug-and-perf operations. Cemented ball drop sleeves were trialed on a three-well pad, and all stages were stimulated successfully. The plug-and-perf operations also had complications when trying to achieve breakdown. With the ball drop system, the ball can be launched and followed immediately by acid, allowing for immediate breakdown. The operator continued to run four wells on a pad, averaging 55 stages of cemented ball drop over a 3,300-m lateral length with 60-m spacing. The liners are deployed on drill pipe, and the PrimeSET liner hanger is set in the intermediate casing after cementing. 

Stimulations were initiated through Packers Plus Toe AP ports for stage 1. The remainder of the stages were ball-activated, and all launch and shift events were verified by the Packers Plus ePLUS Retina monitoring system. After stimulation, the wells were put on production with no drill-out required (dissolvable balls).  

80-Sleeve QuickPORT IV hybrid well. An operator successfully resolved operational issues in extended-reach laterals by deploying ball-activated sliding sleeves for the toe stages of their plug-and-perf completions. This hybrid completion technique deployed QuickPORT IV sleeves in four-sleeve clusters for the first 20 stages of the well.  

The operator had been using plug-and-perf operations but experienced issues with wireline and coiled tubing for plug setting, perforating and providing sufficient weight-on-bit for mill-outs in wells with a measured depth (MD) greater than 6,096 m. The operator began running QPIV sleeves on all wells beyond this point, placing one port per joint. They evolved to wells up to 7,102 m, MD, with lateral sections of 3,719 m. 

A total of 80 QuickPORT IV sleeves, run in four-sleeve clusters, were designed to cover the first 20 stages of the well and the deepest 1,189 m of the lateral. The rest of the well would be completed, using plug-and-perf. All 20 stages were stimulated in under 70 hrs of pumping time, during which the ePLUS Retina monitoring system verified the launching of balls and actuation of the sleeves. The success of this completion proves the effectiveness of the QuickPORT IV sleeves, not only in reducing operational risk for interventions at the toe and saving the cost associated with downtime, but in its ability to perform as a high-stage-count completion solution. 

12-sleeve diffusor set-up deployed in a hybrid wellbore. Using coil frac sleeves, an operator in the Charlie Lake formation evolved to longer lateral lengths beyond the reach of coiled tubing. Coiled tubing could reach to 6,500 m, MD, on a 2,300-m TVD well, but the operator planned to drill to 7,350 m, MD. 

12 stages of diffusor sleeves. The 12 stages were stimulated with ball drop, and the remaining 59 stages with coiled tubing over an 850-m section. The 12-stage ball drop section stimulated well below maximum pressure at the designed frac rate. Higher rates can be achieved without the coiled tubing in the hole, and no drill-out was required. The smallest seat in this case was 76.2 mm, ID. The operator has deployed several systems in this manner and has more planned, which will reach further depths in the near future.  

TECHNOLOGY EVOLUTION 

During the past two decades, as operators continued to develop new fields, maximize recovery and increase stage counts and treatment sizes, completion technology has evolved continuously to meet the needs of operators. 

Sliding sleeve technology helped transform the completions industry nearly two decades ago, and innovation has continued steadily throughout the years to help maximize efficiency. From single-point entry sliding sleeves to hydraulically activated toe sleeves and limited-entry cemented ball-drop completions, each evolution has played a role in advancing completion capabilities by enabling treatment of longer laterals and more stages with more proppant and fluid at high rates, Fig. 5. 

Fig. 5. Subsurface representation of a multiple-stage horizontal completion.

These technology variations and options provide producers with flexibility in developing their particular geology and take into account completion trends, such as extended-reach laterals and high-rate stimulation that provide the potential for increased production at a lower cost. 

With a reputation as the premier ball-drop completion system provider and more than 250,000 stages completed worldwide, Packers Plus has expanded its offerings in recent years to include innovative technologies for a variety of applications and multiple segments of a well completion. The common theme among all these product portfolio additions is they are designed to help producers improve operational efficiency, reduce risk and improve completion programs. Learn more about the company and its advanced multi-stage completion system technology at https://packersplus.com/en 

About the Authors

Mike Kenyon

Packers Plus Energy Services

Mike Kenyon is regional sales manager of Canadian Operations for Packers Plus Energy Services. He has 25 years of oil and gas experience and has been involved in running and designing open-hole multi-stage systems since their inception. Over his career, Mr. Kenyon has also worked in various operational and sales roles.