Well-to-Well Two-Phase Injection using a 10in Diameter Line to Initiate Well Discharge in Mahanagdong Geothermal Field, Leyte, Philippines

Abstract

Most of the wells in the Mahanagdong Geothermal Field need to be induced in order to discharge. This is mainly because the field lies at a much higher elevation of 700-900 mASL and therefore producing wells have a low water level at the wellbore. Added to that is the absence of gas and two-phase pressure build-up in most of the Mahanagdong wells.
To initiate well discharge in Mahanagdong wells with this condition, additional energy must be put into the water column of a static well to convert it to two-phase column and for pressure to build-up. There are several methods use for this purpose, namely; a) air (or gas) compression; b) gas lifting; and c) well-to-well two-phase injection. The most commonly used method at PNOC-EDC fields is the well-to-well two-phase injection.
This paper discusses in details the procedures of a well-to-well two-phase injection using two different diameter sizes of injection lines. Previous practice is done through the use of a 2" diameter injection line connected to the wing valve of each well. Using this line size, injection time is longer, ~ 2 days, with the chances of a successful discharge seldom achieved. In contrast, the use of a 10in diameter line has greatly reduced the time for two-phase injection and improved significantly the chances of a successful well discharge.