TATNEFT Company has successfully drilled wells of small diameter with horizontal wellbore completion.
The wells with horizontal wellbores following the TatNIPIneft design have been constructed for NGDU “Nurlatneft” (productive Bashkirian layer of Ashalchinskoye field) and for NGDU “Almetyevneft” (productive Tournaisian layer of Romashkinskoye field).
The specifics of drilling the horizontal wellbore in a small diameter well are the lack of spare diameter, which is envisaged in case of drilling traditional wells. When drilling traditional wells potential trouble intervals are isolated by the production casing, and then, in the absence of complications risk, the drilling of a horizontal wellbore along the productive section is continued with a drill bit of a smaller diameter.
Modern drilling technologies proposed by the design laboratory of TatNIPIneft, such as geo-steering; application of drilling mud, which strengthens the well walls; mud logging with instantaneous core analysis; drilling of the wellbore buildup and horizontal sections with application of the same bottom hole assembly have been implemented to minimize the risk of complications during drilling.
The logging performed during the wellbore drilling allowed determining the top of productive deposits without drilling interruption. In the frame of a special computer program downhole geo-steering information used to come through the real-time communication channels to computers of the NGDU (Oil and Gas Production Board) Geological Service, where it was promptly processed by specialists.
Following the instruction of the geologists the geo-steering service field engineers have determined the horizontal wellbore build-up ratio with respect to the oil-bearing part of the formation. The drilling was continued without changing the bottomhole assembly. Mud logging data determining the oil saturation of cuttings was used as a guide for the course trajectory correctness.
114 mm production casing equipped with a casing packer (to prevent penetration of cement slurry into the productive horizontal wellbore) was run after reaching the hole target depth. Cementing of the production casing was carried out raising the cement to the wellhead. The reservoir was left open for production with a horizontal bottom.
The works on drilling small diameter holes with a horizontal wellbore completion have been performed by a drilling crew of OOO “Tatneft-LeninogorskRemServis”, while the geo-steering operations have been performed by OOO “TNG-Group”.