The drilling of development wells in layered sand-shale sequence involves thin and sinuous targets. Optimal Drilling and well placement is a requirement for these thin reservoirs in order to drain them in a cost effective manner. A slanted well with 82 deg inclination was planned and drilled to drain oil from the Lower Cretaceous layered sands of target formation as part of a development plan to increase the production rate from the North Kuwait oil field which is aligned to Kuwait Oil Company's (KOC) goal of producing 4 million bbl/d oil by 2020 and sustained it until 2030.
Plan is to build the inclination through the 12 ¼" hole section kicking off with Motorized Rotary steerable system up to 50 deg inclination. The 8 ½" section is planned to build from 50 deg to 82 deg and again planned to be drilled with rotary steerable system and resistivity at bit technologies to allow precise landing with high angle in the required zone of interest. The 6 1/8" section is planned to be drilled with Rotary steerable and triple combo LWD and resistivity at bit technologies to precisely drill through the required zone of interest. The well was planned to be drilled with Rotary steerable tools to enable smooth well profile and avoid micro doglegs to enable smooth deployment of ICD completions through different layers – sand – shale – silt – shale sequences.
After drilling the top hole vertical sections with rotary stiff BHA's and running Casings, the well was kicked off in the 12 ¼" section. The details of the BHA and the performance are as mentioned below.
BHA #01 : 12 1/4" PDC Bit - RSS with 12 1/8" Stabilizers - Flex Collar - 825 MWD - NMDC - 3 × 6 5/8" HWDP- Jar- 6 × 6 5/8" HWDP - 5" DP to surface
This BHA drilled the well from kick off point to the casing point in one run and achieved 54 deg. The section was planned with 3.3 deg DLS and to be drilled with roatry steerable system so as to achieve smooth well bore profile. During the drilling of this section, the bit induced severe Stick & Slip and very high torque throughout the run, Stick & Slip was 100 % and Torque had gone up to 17 kft.lb at surface, When String is picked up off bottom torque goes back to normal (3k ft.lb) and stick slip doesn't exist, Had to pick up too many times throughout the run specially while drilling Mauddud formation because Rotary steerable tool face was unstable and affected by the severe stick & slip. After reaching to the section TD, wiper trip was performed and the casing was run to the bottom and cemented.
BHA #02 8 1/2" : 8 1/2" PDC Bit – RSS 675 - LWD - MWD - NMDC - 24 × 5" DP - 3 × 5" HWDP- Jar- 2 × 5" HWDP - 15 × 5"DP - 15 × 5" HWDP - 5" DP
This BHA continued drilling the section and build from 54 deg to 82 deg at the casing point / section TD. The section was drilled with a dog leg severity of 3.5 deg / 100 ft without any issues. The BHA consisted of both Rotary steerable system and logging while drilling technologies. The rotary steerable system enabled smooth well bore profile and the logiing while drilling (resistivity at bit) enabled the landing opf the well in the required zone of interest. The section drilled and the formation was picked up with correlation done on the off set wells. After drilling the section, the liner was run to bottom without any issues and cemented.
BHA #03 : 61/8" PDC Bit - RSS – LWD -MWD – LWD - 3 × 3 1/2" HWDP -57 × 3–1/2 " DP - Jar-6 × 3–1/2" HWDP -27 × 3-1/2 " DP- 4.75" X-over Sub-3 × 5" DP-12 × 5" HWDP- 5" DP to surface
The BHA consisted of Rotary steerable system, MWD and LWD comprising Resistivity at Bit, formation resisitivy, Density and neutron porosity. The section was drilled holding the inclination of 82 deg to cut through the reservoir layers. Drilling team, field development and well placement teams worked very closely monitoring the formation evalauation measurements whilst drilling through this section and called target depth afer reaching the bottom part of the reservoir. The rotary steerable tool again enabled a very smooth well profile to be drilled.
After drilling the top hole curve sections, well was successfully landed into the target sand channel and drilled through the drain hole section using resistivity, gamma ray and density neutron tools. Well was monitored in real time with a multi task team comprising drilling department, field development, well placement and target depth was called out while it approached the expected zones with water fingering. After the completion of the 6 1/8" reservoir section, achieving very smooth profile with pre – selected technologies, a dedicated roller reamer run was performed to make sure that the hole profile is more precise and smoother for the deployment of ICD completions for the first time in a high angle deviated well crossing through different layers. After taking all the precautions related to hole cleaning, mud weight management to mitigate the shale sections open at high angles and well geometry, well was completed with ICD completions for the first time in Kuwait for a slanted 82 deg well within sand-shale sequence.