Concerns and Solutions for Interfacing Fracturing and Sand Control Completion Strategies into Multilateral Technology
Authors: Cavender Travis , Roane Thomas O. , Restarick Henry L. 
Published: October 2008

Multilateral technology offers the oilfield a completion system that mechanically connects one or more lateral wellbores to a parent wellbore and allows selective or commingled production. These capabilities usually provide more costeffective well construction since reservoir exposure from one wellbore is increased. In offshore and deepwater environments where slot and/or sub-sea templates are limited and rig costs substantially higher, these advantages are even more beneficial. Because of the flexibility of this technique and its capability to offer various production options, it helps to mitigate the risks previously associated with directional/horizontal wells in new field developments as well as in revitalization of mature fields. Continual improvement in drilling techniques and the increase in the number of field successes using multilateral technology have continued to increase its popularity; however, as with all completion techniques, it must be remembered that existing completion options must be evaluated for each case, and if needed, adapted to meet specific reservoir objectives and concerns.

This paper will focus on interfacing sand-control fracturing stimulation with multilateral technology. The techniques targeted include existing, modified, and conceptual completion methods that can be deployed into multilateral field-development strategies. The strategies address window selection, junction isolation, fluid loss, debris management, and lateral accessibility considerations along with the applications, and benefits of specific tool configurations recently developed. Several completion sequences, which include a new Technology Advancement for Multi-Lateral (TAML) level 4 single-trip, gravel-pack methods and installation of expandable screen technology, will also be presented.

Introduction

The benefits of multilateral technology have been well documented around the world as a cost effective alternative to accessing oil and gas reserves. To date, the bulk of these installations have occurred in naturally fractured carbonate reservoirs as well as poorly consolidated sandstone reservoirs. In either scenario, the lateral borehole typically is drilled horizontally so that maximum reservoir exposure can be obtained. Slotted liners or sand screen completions have been very effective for borehole support and/or sand-control devices when deployed in uniform sandstone reservoirs,1 whereas openhole completions are commonly used in carbonate reservoirs with natural fractures.

Fracture stimulation and advanced sand control completion applications can also be implemented into multilateral well planning strategies. Low-perm carbonate reservoirs can be effectively stimulated using traditional stimulation designs normally performed in single wellbore applications. The junction isolation tool configuration will vary and depend predominately on the TAML classification of the junction as well as whether the stimulation job is pumped down the casing or the tubing work string. In addition to isolating the junction from the stimulation-treating pressure, the tool configuration should also have capability to provide well control and zonal isolation. This will allow multiple lateral legs to be individually stimulated from a single parent bore and will eliminate the need for kill-weight fluids after each zone is stimulated and unloaded.

In sandstone reservoirs that require gravel packing or fracand-pack applications, the completion tool configuration for the mainbore and lateral completions will differ. The mainbore completion below the junction can normally deploy traditional sand-control equipment.