Abstract:

The gas production in high-temperature, high-pressure (HTHP) projects in the Nam Con Son basin is entering a declining production phase, the production duration almost reaching the final phase of the designed field life. Therefore, the need to build a development plan for maintaining and supplementing gas production is the most important in the current phase. Evaluation of gas field conditions, drilling infill wells to expand existing prospects is considered a feasible solution both technically and economically. However, the physical characteristics of the production reservoirs have changed after a long production time, including a decrease in pore pressure at the production reservoirs, posing a significant technical challenge during the drilling operations. The infill wells are required to penetrate through the shale formations interbedded with sand formations. In there, the cap rock shale layer remains at or close to virgin pressure and the sand reservoir with pore and fracture pressures has largely decreased due to production activities. There is no mud-weight window that exists any more at the transition between cap rock and reservoirs which leads to drilling problems such as loss circulation, gas kicks and especially, the well could not reach the total desired depth or production targets which impact to overall development project. This article evaluates the applicability of a combination of technologies, including utilizing special lost circulation materials to seal the fractures due to changes in reservoir properties and the application of managed pressure drilling methodologies while drilling through infill wells in HTHP conditions. The goal is to minimize the risks of well problems and provide the management of uncertainties during the drilling which improves project efficiency.