The Shuaiba formation in the Raudhatain field is a highly fractured limestone reservoir. Conventional drilling technology in this formation usually results in a complete loss of drilling fluids to the formation. These losses cause severe formation damage which results in masking the evaluation of the potential for hydrocarbon production.
Underbalanced Drilling Technology was proposed as an alternative drilling method. The main objective of the UBD drilling application was to evaluate the potential of hydrocarbon in the Shuaiba formation while simultaneously eliminating fluid loss to the formation and improving drilling performance.
This well was the first well drilled underbalanced by KOC, a training program was prepared in order to familiarize the rig personal involved with the operation of the UBD equipment and procedures. The openhole section was drilled out of a 10 ¾" casing with an 8 ½" bit. A conventional mud pulse MWD/PWD/LWD tool with real-time annular pressure, temperature and gamma ray sensors were incorporated in the BHA. The use of MWD/PWD/LWD provided a means of monitoring the downhole underbalanced conditions and formation properties while drilling. The Shuaiba formation was successfully drilled underbalanced without any fluid loss during the drilling phase. The openhole section was drilled to a total depth (TD) of 8942 ft MD, with an openhole length of 242 ft.
Integrated efforts of KOC and service companies of various disciplines during planning and operation stages of the well led to the success of the project. No QHSE incidents were reported.
This paper highlights the key factors in the underbalanced drilling design phase, the operational challenges faced, and the results of the first well drilled in Kuwait using underbalanced drilling technology.