Selecting a Development System for Offshore Coastal Gas-Condensate Fields

Abstract

A case study of a gas-condensate field located on the northeastern shelf of Sakhalin Island demonstrates the possibility of development of condensate-containing gas reserves by drilling very long ERD wells (drilling from the shore). The development system described in the paper includes drilling well with upward orientation. Such design provides complete cleaning of a wellbore from fluids and solids accumulated over a long period of maintenance-free operation. The choice of a development system using horizontal wells is also associated with the geological structure of the field (massive type accumulation with a single gas-bearing contour is broken by tectonic faults into separate blocks with different hypsometric elevations). Under the technical, economical (drilling from platform and from land, the use of subsea production systems, ice gouging with hummocks), and environmental (presence of valuable fish species in water areas and permanent residence of indigenous peoples) limitations, the development of individual wells with vertical completions turned out to be unprofitable. For the first time for this type of accumulation located in a coastal zone, a unique method of monitoring the recovery of reserves within the cross-section, as well as movement of the gas-water contact without the use of monitoring and pressure observation wells was suggested.