|dc.description.abstract||With the notion of evolving current Extended Reach Drilling, this master thesis examines if drilling 20–40km is feasible. Several reservoirs offshore in the area outside of Lofoten in the northern part of Norway are reachable by 20–40km in horizontal displacement. The term for these excessive lengths is Ultra Extended Reach Drilling (UL–ERD) and is the foundation for this master thesis.
To solve this task a "‘Well Path and Drilling Software"’ (WP&D software) is developed to simulate the drilling operation with regard to well path, drilling, running of casing/liner and well service using wire line. Three–dimensional well path design, analysis of loads and stresses experienced, torque and drag calculation and hydraulic calculation used in the software are presented in this master thesis.
Attaining UL-ERD demands innovation in all areas of drilling technology. This thesis addresses this by simulating different scenarios in the software, presenting and discussing the results. The well path designed needs least possible dog–legs and azimuthal change to avoid increased frictional forces and contribution from the capstan effect. Drilling with different drill pipe materials like steel, titanium and composite shows the advantage of using lighter materials to reduce torque and drag. The hydraulic requirements to pump down the string is overcome by having 700 bars of working pressure available on mud pumps and the use of large inner diameter of drill pipe. High Equivalent Circulating Densities (ECD) are handled by Managed Pressure Drilling (MPD) and its Applied Back Pressure (ABP).
The flow rate used to maintain a constant annular velocity is valid if hole cleaning is fulfilled throughout the well. Larger inner diameter requires larger outer diameter which leads to excessive ECDs in small holes. Large diameter drilled holes with corresponding casing/linerOD sizes in parenthesis; 36"(30"), 26"(20"), 17 1/2"(13 3/8"), 17 1/2"(13 3/8" and 12 1/4"(95/8"). Expandable casing is used to have two lengths of 13 3/8" liner intervals giving the ability of using large inner and outer diameter drill pipe.
Setting of casing/liner is performed conventionally using casing/liner filled with mud and unconventionally with fully evacuated casing/liner with nitrogen or casing/liner with mud over nitrogen. The snubbing unit is assumed dimensioned to handle 100 tonnes to get casing/liner down. Rotation of the liner is possible when the absolute density is close to the mud weight in the hole, giving a reduced buoyant weight.
Different simulation of inner and outer diameter dimension of drill pipe concludes that an 8"outer diameter and 7" inner diameter is the best option for UL-ERD in this thesis. This, incombination of a lighter material such as composite, leads to 40882 meters Measured Depth(MD) at 2506 meters True Vertical Depth (TVD), Horizontal Displacement (HD) of 39501meters and a Step–Out–ratio of 15,7. It also has a slight azimuthal change in the well path.The mud pumps deliver 700 bars and the proper flow rate to clean the wellbore using MPD.The casing/liner reaches setting depth and it is possible to run composite wire line with welltractor to perform well service, through the production tubing. Torque and drag calculationsare valid for the specified Make-Up Torque (MUT) of approximately 85kN. The max limit of100kN MUT can be handled by using a tapered drill string.
5 7/8" drill pipe with either steel, titanium or composite can be used to drill multiple wells and join them together to achieve one UL–ERD well. Steel drill pipe is be most preferable with regard to availability and cost. Larger tubular with light drill string material is beneficial when it comes to reducing torque and drag and hydraulic issues in these shorter wells. Obtaining UL–ERD wells in this way requires less modification with regard to the drilling process, since lengths drilled are shorter. The disadvantage is that in a somewhat pristine area as Lofoten, the Health Safety Environment (HSE) issues with drilling offshore is a valid obstacle for not choosing this solution here.
This thesis recommends that when having solved the issues with torque and drag, hydraulicrequirement and available equipment, reaching UL–ERD can be performed by drilling fromone location on land, or with multiple wells from several locations on and off land joined into one well. An 8" composite drill pipe with 7" inner diameter could be used, lightening the casing/liner to get to setting depth and use composite wire line to perform well service.Recommendations are made on the basis of mud pumps delivering sufficient pump pressure,stronger snubbing units, use of expandable casing, torque and drag is being handled, large hole diameters, larger inner and outer diameters of tubular, the use of a tapered drill string,development and innovation of equipment found vital for the task.||nb_NO