Filter with Pre-Packed Gravel
A filter with two filter elements made of spirally wound wire, with gravel packing between them.
Advantages
- Anti-erosion protection. The technology is especially in demand in weakly consolidated reservoirs prone to failure and intensive sand production — the gravel layer stabilizes the bottomhole zone, prevents rock washout and protects the well structure from erosion wear caused by high-velocity fluid flows.
- High strength factor of the slotted screen and structure. The robust design withstands significant pressure differentials and mechanical loads during run-in and operation, preventing slot deformation and failure of the unit, while reliable fixing of the gravel pack prevents its displacement and loss of filtering properties.
- Effective protection against sand production. The gravel layer acts as a barrier: it retains fine reservoir particles (including silty and fine-grained sands) through the “arch effect” in the gravel structure. This prevents sand from entering the well and protects downhole pumping equipment from abrasive wear.
- Reduced well-construction time and cost. Unlike conventional gravel packing, where gravel is pumped into the annulus at the field, here the pack is already made at the factory. This eliminates the need for special equipment (e.g. a frac fleet), simplifies completion operations and cuts costs — in some cases completion cost can be reduced by about 20%.
- Flexibility for completing complex wells. Filters with a pre-installed pack can be run into long horizontal boreholes (over 1000 m) and the interval can be segmented with swelling packers. This makes it possible to adapt the completion to heterogeneous reservoirs and optimize production.
- Regeneration and maintainability. The filtering surface can be restored by direct and reverse flushing, which helps combat plugging (pore clogging) and extends the filter’s effective service life.
Specifications
- filter element length: 2400/6060 mm
- filter element slot gap: 150 µm
- performance class: V3
- quality class: Q2
- size range: 73/114; 114/178; 140/245
Application area and experience
- Oil and gas production from weakly cemented reservoirs. This is the main application: formations composed of loose sands fail easily under pressure differentials, and the filter prevents collapse of the reservoir skeleton and sand production.
- Horizontal and multilateral wells. The technology is in demand where it is important to ensure uniform fluid inflow along the entire filter length and to avoid local sand-production zones.
- Fields with a high content of fine fractions. If the reservoir contains more than 10% of fine and silty particles, ordinary slotted or mesh filters cannot cope, whereas gravel packing provides finer and more reliable cleaning.
- Offshore and remote fields. Here it is critical to reduce operation time and minimize the amount of special equipment on site — a pre-installed pack achieves exactly this.
- Wells with complicated operating conditions. For example, under sharp drawdown fluctuations, high flow velocities or a risk of bottomhole-zone erosion: the gravel layer reduces the erosion effect and evens out the inflow profile.
- Water-intake wells in loose sand horizons. In hydrogeology such filters are used to protect water intakes from silting and sand production, ensuring a stable supply of clean water.
