Abstract
This paper presents a case study of designing a lower completion deployment concept consisting of conformance control liner with up to 25 compartments (packers and sliding sleeves). The horizontal well was planned with the longest lateral section of up to 2,500m in an out-board area of Tengiz field. The reservoir in this area is known to have a modest carbonate matrix reservoir, relatively poorly connected with presence of scattered natural fractures networks. To maximize number of natural fracture intersections and contact with reservoir matrix, Tengizchevroil (TCO) planned to drill a horizontal well with long lateral section, followed by frac and/or matrix stimulation to improve production by connecting to the natural fracture network.
One of the main challenges of the well design was the ability to successfully deploy a lower completion to the well total depth (TD). Extended length of the lateral section causes drag accumulation along the string during the run which could lead to inability to run the liner to the desired depth. Generation of excessive compressional loads which could result in liner string buckling and ultimately to lock up was expected at open hole friction factors more than 0.45. Based on friction factors calibration from the other Tengiz offset wells with similar well trajectories which revealed 0.35–0.45 OH FF along with the absence of experience in running long completions strings with up to 25 compartments and lack of good understanding of OH FF in naturally fractured horizontal well, the decision was made to deliberately plan for 0.60 OH FF as design friction factor to establish feasibility.
Installation of the liner in this well at higher OH FF required consideration of advanced methods such as a) liner flotation, b) liner rotation, c) running a casing swivel. The detailed analysis of each of the methods revealed that introduction of liner rotation would not only solve the liner running issue on this well with long lateral section but may also allow completion of more extended lateral sections beyond 2,500m.
