Multilateral wells proliferate as operators reap rewards

In the oilfield, as elsewhere, history repeats itself. Multilateral wells have become the latest overnight success, with wells of every complexity level and varying numbers of laterals being drilled daily throughout the world. One expert recently commented: “Ten years ago, a well team had to justify the decision to drill a multilateral rather than a single wellbore. Today, they must justify the decision not to drill a multilateral.”

Just as was the case with horizontal drilling, 3D seismic and other breakthrough technologies, industry adoption of multilateral technology was not actually an overnight phenomenon. Instead, it occurred through years of incremental improvements and credibility-building successes. In this case, what began as a vision to conserve slots on deepwater platforms gained its first significant commercial success in mature fields. The final breakthrough came with a surge in the demand for, and price of, oil and gas that made it incumbent upon operators to absolutely maximize hydrocarbon production. Now, with a track record of reliability and the integration of intelligent and expandable completion technologies, multilaterals have moved into the mainstream of oil and gas field development by proving their ability to access more reservoirs in less time.

Unlocking value in Alaska

Baker Oil Tools’ TAML Level 3 HOOK Hanger system has enabled operators on the North Slope of Alaska to significantly increase production while reducing well costs and risk. An excellent example is the US$179 billion Milne Point Schrader Bluff S-pad extension project, which is the first North Slope large-scale development to be entirely based on the use of multilateral producers. From 1987 to 1994, traditional completion technology and various sand control techniques in the heavy oil Milne Point field yielded initial production rates of 300bopd.

The world’s first 4½ inch x 7 inch HOOK Hanger Level 3 system was installed in the field in 2001. The HOOK Hanger system provides mechanical support for junctions that join cased and cemented main bores with screened, open hole laterals in wells with commingled production. In Milne Point, it allows the junction and slotted liner to be set together in one run and offers the option for re-entry into both the lateral and the main bore. Here, HOOK Hanger multilaterals have averaged initial production rates of 1600bopd, with one well producing 3200bopd in its first test.

HOOK Hanger systems also proved valuable in the North Slope’s West Sak development. In one well alone, the operator was able to reduce the number of trips by 50 percent and save 108 hours of rig time, for estimated cost savings of US$360,000. At the same time, some wells production increased 280 percent over that of a conventional single well.

New life for Glitne

For the North Sea Glitne field, combining advanced multilateral and intelligent well technologies has enabled operator Statoil to increase production, tap additional reserves and control water production.

The FORM 5 is the world’s first corrosion resistant alloy (CRA) re-formable multilateral junction and the first re-formable designed as a completion template, rather than a drilling template. The Level 5 system consists of a main bore and two cased legs, of which one is pre-formed. The system is deployed in casing and then re-formed in a casing window using expandable metal technology. The system provides a mechanically sound Level 5 junction with integral hydraulic integrity. Re-forming the leg in the casing window increases the branch/parent diameter ratio and, thus, effective flow area. The system can be integrated with various conventional cased and open-hole completion methods, such as gravel packs, screens and liners, and with final completion designs such as intelligent well systems.

In the Glitne A-6H well, the FORM 5 system was integrated with Excluder sand control screens in each lateral and completed with a Baker InForce intelligent well system in order to remotely control flow from the lateral at the junction, without rig intervention, in anticipation of eventual water breakthrough. Additionally, Baker developed a multiplexing device known as a Single Line Switch (SLS) to allow a single hydraulic line to run to surface and ensure that running time for the intelligent well would be similar to that of a conventional completion.

The final result was a dual lateral well with remotely controlled lateral production that would have been uneconomical to drill and complete from the sub-sea tree using a conventional configuration of two single laterals.

Making heavy oil attractive in Oman

For Oman’s Mukhaizna field, heavy oil, unconsolidated reservoir sand and potential early water breakthrough posed technical difficulties and high costs that precluded early development. A subsequent, dedicated field appraisal and application of advanced drilling and completion technologies transformed the field into an attractive investment opportunity. Using a HOOK Hanger multilateral system, Centrilift electric submersible progressive cavity pumps (ES-PCPs), a Baker Payzone external casing packer, Model D production packers, and an InForce intelligent well system, Petroleum Development Oman (PDO) brought the Mukhaizna 64 well on line at an initial production rate of 470bopd , which was significantly better than expected.