豪州沖イクシスガス田海洋掘削におけるライザーレスマッドリターンシステムの使用実績

Abstract

INPEX Browse Ltd. has drilled 6 wells in the Browse Basin in order to appraise the production permit WA-285P from 2000 through 2004 (at the 1st and 2nd Drilling Campaign). All of wells have encountered stuck pipe problems while drilling the unconsolidated Grebe formation sandstone and they have provided a lot of Non Productive Time (NPT) due to fishing or sidetrack. According to the desk top study of Grebe, which was performed after drilling in 2004, it was concluded that the stuck pipe problems result from the collapse of unconsolidated sand, in other words, such collapse is caused by the absence of an effective filter cake capable of stabilizing the well bore. Eventually, INPEX Browse Ltd. has decided to drill the unconsolidated Grebe formation sandstone by closed circulation system using drilling mud instead of Seawater.In order to achieve this objective, Riserless Mud Return (RMR) system was introduced by AGR (Norwegian Company) before 3rd Drilling Campaign. Through this system, all three (3) wells have been successfully drilled without any hole collapse and no NPT was recorded. That is a major improvement rather than last two (2) drilling campaign and RMR system was demonstrated as one of an effective procedure to drill unconsolidated formation in Browse Basin.