An operators renewed focus on horizontal well drilling and open hole completions, using Inflow Control Device (ICD) screens, necessitated the use of oil-based drill-in fluids (DIF) to drill and complete their reservoir. The challenges were increased by low reservoir pressure conditions, increasing the risk of drilling fluid invasion and possible reservoir damage. Comprehensive laboratory studies were carried out to evaluate DIF performance and ensure understanding of the possible damage mechanisms produced while drilling, considering the reservoir characteristics and drilling conditions.
The customized near-wellbore damage remediation system, with a delay-reaction, was designed based on Mesophase technology. This paper discusses detailed laboratory analysis for the clean-up system and its field applications in Kuwait horizontal wells. The applications included drilling carbonate and sandstone reservoirs, open hole ICD completion, and performing effective cleanup required for maximum production.
The effectiveness of the Mesophase clean-up system to remediate reservoir damage and improve producibility was evaluated immediately after well kick off and again after steady production levels were reached. This paper shows the results obtained after the application of the near-wellbore remediation technology.
The lessons learnt during the Mesophase application were incorporated on upcoming wells to standardize the operating procedures and improve field performance.
To meet production targets from Raudhatain field, the operator initiated a horizontal well drilling campaign with open hole ICD completions in Mauddud (Carbonate) and Burgan (Sandstone) reservoirs. The ICD screens control flow rates across the completion for the entire length of the interval. This approach dramatically reduces the effect of water and gas breakthrough, while optimizing production rates across the full completion interval.
Challenges encountered during drilling these horizontal wells included increased non-productive time resulting from interbedded formations with varying formation pressures, wellbore instability in the reactive and stressed shale sections and hole cleaning issues. An oil-based drill-In fluid system was designed with a high oil water ratio (OWR) to overcome these challenges and protect the reservoir from drilling fluid damage.
The formation damage mechanisms analyzed included:
Foreign particle invasion
Formation clay swelling
Chemical incompatibility
Oil wetting of the reservoir rock
Emulsion blocking
Fluid invasion (Water Blocking)
