With an estimated 70% of mature and deepwater oil and gas wells requiring sand control and experiencing costly challenges, there is global interest in finding new, efficient solutions to downhole sand control.

Achieving sand-free flow performance in openhole completions often requires removal of the annular gap between the screen section and wellbore. For the first time in the industry, patented hydraulic screen technology has been used to overcome the challenges associated with the high failure rate of traditional gravel packing methods, which are time-, labor- and logistically intensive and costly.

Darcy developed the hydraulic screen technology installed in Statoil’s Statfjord oil field in the Norwegian Sector of the North Sea. This openhole application, in a wellbore faced with continuous reservoir pressure depletion, contributed an approximate 30% reduction in overall completion time compared to traditional methods. The technology is suitable for a range of applications, including mature and low-pressure reservoirs, HP/HT conditions, deepwater and shallow reservoirs, injector wells, horizontal and multilateral wells, and in oil fields with heavy and viscous oil.

Gravel packing challenges
Gravel packing is a proven practice and has been a method used by the oil and gas industry for many decades. It provides a downhole filter designed to prevent the mobilization of formation sands.

The wellbore is supported and formation sand is held in place by a gravel pack that is pumped downhole from the surface; a screen is first deployed across the reservoir interval and sized to retain the gravel beingpumped. The particle size distribution of the formation sand is analyzed to determine the gravel size to prevent unwanted sand production while achieving the desired production or injection performance.

The gravel pack method is time- and labor-intensive and operationally challenging; it typically requires a crew of more than 10 people for an average operation, with extreme demands placed on HSE and logistical planning, especially offshore or in remote locations.

While gravel packing has historically proven to achieve excellent results in many environments, the industry is increasingly faced with marginal economics combined with reservoirs and applications where technical difficulties occur when pumping the gravel pack. One particularly challenging area is mature low-pressure environments where successful placement of a gravel pack depends on the ability to maintain circulation without excessive losses occurring to the reservoir formation. If losses are too high and circulation cannot be maintained to place the gravel, there is an increased risk of incomplete packs resulting in compromised well performance and/or well failures.

An unsuccessful gravel pack fails to remove the annular gap between the screen and wellbore, leading to a risk of sand being free to travel as the well is opened to production (or injection). This mobilization of sand can result in erosion of downhole equipment and/or plugging of the completion, which ultimately can lead to severely impaired well performance, loss of equipment integrity or complete completion failure.

Alternative sand control
Hydraulic screen technology was developed to set a new benchmark in operational efficiency by removing the need for pumped sand control, greatly reducing the associated time, labor, and operational and logistics costs. Hydraulically activated from the surface, a maximum crew of two is required offshore for an operation using standard rig practices.

The screens are designed to integrate fully with standard completion equipment and rig handling operations. After deploying to setting depth, the hanger and screens are set by surface-applied pressure from the rig cementing unit; this operation typically only takes 1 hr. Once set, the screens extend radially to close the annular gap and provide positive wellbore support. The technology suits well designs with 8.5-in. drilled openhole reservoir sections and extends to a maximum range of 10-in. wellbore diameter. The hanger packer is set and reservoir isolation barrier closed in the same trip, providing testable barriers prior to displacing the well for upper completion operations.

Rig time is greatly reduced with the removal of steps from the well program for circulation and displacement of specialist fluids for gravel pack pumping operations. The screen design provides mechanical strength and high collapse resistance for applications where severe geomechanical changes might occur or where extreme production conditions exist.

The strength of the completion is therefore maximized, its large internal diameter retained throughout to ensure life of well operational efficiency; well intervention functionality; and options for selective production, injection and internal and external isolation and shutoff.

Applications
The screens are suitable for all sand control applications but are particularly suitable for offshore, remote or environmentally challenging locations.

The recent Statoil installation involved a mature offshore environment faced with continuous reservoir pressure depletion. The producer well was drilled to 2,580 m (8,465 ft) at a maximum deviation of 30 degrees and at a temperature of about 80 C (176 F).

The technology is designed to complete complex wells with less risk such as horizontal and multilateral wells. Extended-reach drilling also poses an issue when the operator may want to step out to reach a pocket of the reservoir. This can create a challenge to pump and circulate a gravel pack and increase risks and costs associated with excessive tripping in time.

In regions such as the Gulf of Mexico, where deepwater fields with shallow reservoirs exist, gravel packing is particularly challenging since wells have a small window between the pore pressure and fracture gradient. These geologically young formations make it more difficult to circulate the gravel into position due to the risk of fracturing the formation and resultant loss of fluid leading to an incomplete gravel pack.

In HP/HT wells, the screen’s strength is maintained and risk of mechanical failure is reduced despite high reservoir depletion pressures and geomechanical loading of the openhole screen completion. In all cases, the screen technology closes the annular gap without weakening the original mechanical properties of the screen.

In injector wells, the screens maintain positive borehole support and near-wellbore stability at all times throughout injection and shut-in cycles, providing protection from water hammer effects. The technology prevents problematic resorting of sands and protects injection performance from the outset by effective placement of filter cake treatment before screen activation. It offers additional benefits through effective zonal selectivity as well as ease of well intervention.

Artificial lift in heavy and viscous oil applications stresses the reservoir and is more likely to draw in formation sand. The screens offer positive wellbore support and completion strength, ensuring sand integrity when greater drawdown loadings occur.

Future of sand control
The production of sand into a wellbore and its effects on well productivity, completion and surface equipment is one of the oldest problems facing the oil and gas industry. In a climate of increasing cost pressures, the development of reliable sand control technology that delivers efficiencies is a growing priority. Using hydraulic screen technology as an alternative to gravel packing methods removes reliability issues in wells where annular gap removal is needed. Elimination of operations, planning and logistics required for heavy pumping equipment and a pumping crew greatly reduces costs and minimizes risks.

Offshore