Frac-Hook multilateral system incorporates the field-proven SLZXP liner hanger packer, the HOOK Hanger multilateral junction, a seal bore packer, and a set of unique frac diverters. The Frac-Point system in both legs allows selective isolation of fracture intervals, eliminating the need for a cemented liner and the time-consuming plug-and-perf fracture method. (All images courtesy Baker Hughes Inc.)

One of the most exciting technologies for lowering costs and maximizing reservoir drainage is multilateral systems. This technology is now being applied around the world in applications such as subsea, land, heavy oil, tight gas, and deep water. Once reserved for unique applications to grab the last pocket of oil, clients in the North Sea, Middle East, North and South America now plan complete field developments using multilateral systems.

To provide parity when comparing multilateral systems, a classification system was developed by TAML (Technology Advancement for Multilaterals), a consortium of operators and service companies. The classification system divides wells into levels based on junction functionality. By TAML’s definition, only Levels 5 and 6 provide pressure integrity at the junction. However, Level 5 requires a complex configuration of isolation packers to isolate the junction to provide pressure integrity. Level 6 multilateral completions, in contrast, are much simpler in design and implementation. Levels 1 through 4 do not provide pressure integrity at the junction, and
of these, only levels 3 and 4 provide mechanical support at the junction. Note that the first Level 3 configuration did not provide a lot of functionality since it was typically just a liner anchored back to the main bore, which limited reentry only to the lateral. As a result, one had to move up in TAML level to obtain the desired functionality of reentry into both the lateral and main bore.

Pressure integrity at the junction

Most multilateral applications fall into two simple groups: wells that require pressure integrity at the junction and wells that do not require pressure integrity at the junction.
For maximum functionality in both groups, the focus is on developing Level 3 (pressure integrity not required) and Level 6 or Hybrid Level 5 (pressure integrity required) multilateral systems.

One of the newest developments is the Baker Oil Tools multilateral HOOK hanger casing fracturing system, which recently saw a successful first trial run in a North America land well. The system is a TAML level 3 or 4 junction with full mechanical support of the junction area. It provides pressure isolation at the junction during fracturing operations which is unique for these mid TAML level multilaterals.

This new multilateral system was specifically designed to exploit tight gas reservoirs. One of the trial objectives for the operator was to see if a multilateral system could be drilled and completed at a cost less than that of drilling two single wells in the same field.

Another objective was to see if the production results would match or exceed the expected rates from two separate single wells.

Precise fracture placements

Producing gas in tight shale formations often requires major pumping investments to accomplish the desired results. Traditionally, an operator did not have very many good choices when it came to fracturing a tight gas reservoir. One option was to simply pump fracturing fluid at high pressure into the open hole and hope for the best. This unfortunately resulted in the fracturing fluid flowing mainly to the area of least resistance, reducing production enhancement along the remainder of the well bore. The new system allows operators to accurately place fractures and provide greater access and control of the laterals.

The system also has the advantage of not requiring cementing, which can significantly impact the productivity of the reservoir. It also provides full mechanical support of the junction area and allows deployment of the frac hook hanger with diverters in one trip, which saves rig time. Compared to typical operations, the new system’s smaller footprint, less rig time exposure, reduced pad and slot use lower health, safety, and environmental risks, which is another significant benefit.

One of the key parts of the multilateral system is the Frac-Point openhole fracture completion system, which consists of four primary components: the liner top packer, openhole isolation packers (mechanical or reactive element), frac sleeves, and pressure actuated sleeves. In the upper lateral, the system uses the S-3 HOOK hanger for mechanical support and selective re-entry access of the junction. Hydraulic isolation of the main bore is achieved by installing a liner hanger packer on top of the HOOK hanger. Lower main bore isolation is achieved by the placement of a permanent production packer as well as a main bore frac diverter. Both the lower and upper laterals employ the fracture completion system.

Turning single wells into multilaterals

There are just a few additional steps required to turn a single well into a multilateral well. A one-trip whipstock is used to mill the casing exit window and create enough extra hole to run directional drilling assemblies to drill the lateral. Once the window is complete and the whipstock is retrieved, installation of the ML junction can begin. The fracture completion system is run below the HOOK hanger as part of the liner assembly, which eliminates the need for cementing and perforating operations. Upon reaching setting depth and anchoring the HOOK hanger, the well is left ready for back-to-back stimulation operations.

The key advantages to using the new system in this application are the ability to achieve full mechanical support of the junction area and to deploy the Frac Hook hanger with diverters in one trip, saving rig time. The system allows building of multilateral junctions while permitting back-to-back stimulation of the well. These advantages combined with rigless operation reduce overall fracturing costs.

Lower cost unconventional gas

All objectives were met in the trial well. The operator saved more than 17% on drilling costs and saved an additional 15% on completion costs. Even more exciting was the initial production result, which exceeded expectations compared to offset wells. This trial well proves Multilateral completions have a strong economic potential in unconventional gas developments.

The growing interest in multilaterals during the current downturn and the ability to reduce costs by building multilateral junctions to allow back-to-back stimulation will be a key motivator to accelerated use of this technology in the industry. Operators can save capital investment as well as operational cost by accessing production from two, three, four, or five laterals while drilling a single vertical well bore. Greater drainage access across a section is also possible using this technology. This new system will provide operators with better control of stimulation procedures while offering significant cost savings through the system’s ability to conduct simultaneous operations.