Key Technical Requirements for Well Completion Operations (Drilling & Completion Phase)

In the high-stakes environment of drilling and completion operations, strict adherence to technical procedures is paramount for ensuring wellbore integrity, preventing downhole complications, and achieving operational safety. Based on authoritative technical specifications, the following are critical requirements for key phases of the operation, from drilling out to final well completion.

Pipe tripping is a critical juncture where well control and borehole stability are at high risk. The following measures are mandatory:

• Wellbore Cleaning:​ Prior to pulling out of hole (POOH), circulate drilling fluid for a minimum of two complete cycles to ensure a clean wellbore and uniform mud properties. The density difference between inflow and outflow should not exceed 0.02 g/cm³.
• Safe Circulation & Tool Movement:​ While circulating, keep the drill string 3-5m off bottom. Maintain low RPM (e.g., ≤30 RPM for electric rigs) and move the pipe intermittently over a stroke exceeding 3m. The pipe must not remain static for more than 3 minutes.
• Managed Tripping Speeds:​ Control tripping speeds in the pay zone and the 300m interval above it to prevent swabbing (which can induce inflow) and pressure surges (which can fracture the formation).
• Continuous Hole Fill:​ Regularly fill the hole with drilling fluid while tripping. Typically, fill every 3 stands of drill pipe or 1 stand of drill collar. For wells with high gas readings, losses, or formations prone to collapse, continuous filling is required. While running in hole (RIH), fill the drill string internally every 10 stands to protect float equipment.

If overpull or drag exceeds normal limits (e.g., 10 tons POOH, 5 tons RIH), or fluid backflows, operations must stop immediately. The string should be returned to its neutral weight position. Re-establish circulation with a low flow rate, then ream or backream with low weight and RPM. Once free, continue reaming/backreaming for at least 100m and circulate for one full cycle. If formation collapse is suspected, the hole must be worked to bottom, mud conditioned, and a short trip performed. Heavy/viscous pills may be needed to seal troublesome intervals before final POOH.

Logging presents unique risks, especially with tools in the hole and the well static.

• Preparation:​ Before POOH for tool-conveyed logging, run a drift gauge to ensure tool passage. Record and photograph all tool strings. Ensure wireline cutting tools are readily accessible on the rig floor.
• Well Control Prevention:​ Keep the hole full. For wireline logs, fill after each run. For pipe-conveyed logs, fill the annulus every 3 stands POOH. A float valve must be installed in the work string. Logging must be halted and the hole circulated if the total estimated job time nears the well's calculated "safe period" (based on gas migration rates).
• Emergency Response:​ In case of a kick:
• Wireline Logging:If the tool is near surface, retrieve it and run pipe to shut in. If not, the wireline must be cut immediately using a T-cutter, and the BOPs closed (possibly using the shear rams).
• Pipe-Conveyed Logging:If a side-door sub is out of the hole, install a float and shut in. If the sub is still downhole and cannot be retrieved in time, secure the wireline to the pipe with a clamp, cut it below the clamp, lower the clamped point below the rams, and shut in.

A wiping trip is essential to verify hole condition and stability before running casing.

• Principle:​ No open hole should be left static for extended periods. After logging or if the well has been static for 24 hours (12 hours in horizontal sections), a clean-out trip is mandatory before running casing. The drill string should be pulled back into the previous casing shoe to wait, not left in the open hole.
• BHA Configuration:
• For vertical, directional, and oil horizontals with lateral lengths ≤1200m, a single-stabilizer BHA​ is typically used.
• For longer laterals (>1200m) or all gas horizontals, both a single-stabilizer​ and a dual-stabilizer BHA​ are run successively to verify gauge hole. Stabilizer sizes are critical: the primary stabilizer must be larger than the casing centralizers but 3-5mm smaller than the bit.
• Key Practices:​ Use a roller-cone bit (no nozzles) in high-angle and lateral sections. Ream carefully through known problematic zones (coal, brittle shale). Engineers must review wellbore tortuosity/dogleg severity (DLS) data and be present to supervise reaming through tight spots. Before POOH, perform a short trip to confirm hole is clear. Condition the mud, adjusting properties (density, viscosity, yield point) to compensate for circulating pressure loss and improve cuttings transport. For wells completed with sliding sleeves or horizontals, pump a lubricating/spacer pill into the deviated section before POOH.

The transition from drilling to completion is a systematic process where meticulous attention to procedural details-from managed tripping and rigorous hole filling to proactive well control during logging and thorough clean-out trips-directly impacts operational success, well integrity, and ultimate safety. These protocols form the bedrock of efficient and incident-free well construction. For more detailed information, please don't hesitate to contact Vigor team for more detailed product information.