This paper discusses the economical, operational and environmental aspects of the reduced hole size drilling now used in offshore operations in Gupco and other major petroleum companies operating in the Gulf of Suez Area Egypt. The results demonstrate that reduced hole size drilling saves cost : use of slim hole reduces time related intangible savings, fixed tangible savings, and tangible equipment savings.
The advantages of smaller hole size and the reduction in the volume and size of oil wet drilling cuttings help minimize the environmental impact associated with the use of oil base mud. The reduction in drilling fluid volume and treatment cost, higher rates of penetration, better hole cleaning capabilities, savings in consumables (such as bits, mud, cement and diesel oil), less tangible cost, and easier equipment mobilization are interacted to produce significant operational gains. This results in savings of 40 to 50 percent of well costs versus the cost of conventional wells drilled in the same area.
Although substantial saving were realized, there are elevated risks with the major one being the lack of a good contingency in the event unexpected hole condition or geological condition require an extra casing to be run prior to reaching the total depth. Drilling 6" hole size (or less) for long sections is difficult. Usually, very slow drilling ROP is associated with erratic directional responses, and can restrict use of MWD tools. Moreover, more drill string failures are likely to occur.
Effective preplanning between the drilling, exploration, and engineering to accurately define possible geologic targets and their potential drilling problems can minimize these risks associated with drilling slim holes and provide higher levels of success in meeting objectives.
in summary, slim hole drilling offers significant operational and environmental advantages. And cost savings relative to the conventional well design were realized in the Gulf of Suez - Egypt.
A complete study to determine the economic benefits of the slim hole well program used in the exploratory well Tanka-3
This study shows that the slim hole well program saved approximately $476M relative to drilling the well with a conventional well program.