The operator was drilling their first high-pressure high-temperature (HPHT) exploration well with narrow pressure window in a swamp area of East Kalimantan. The gas field was discovered in 1977 and production started in 1990. Since then, more than 1500 wells have been drilled in this area yielding a total gas production of 9.7 Tcf. Currently T field enters established mature field status which has quite marginal reserves. Therefore, further exploration is seen as one of the solutions to locate additional reserves to enhance overall gas production. The well was drilled directionally with no offset well nearby. While drilling the 6-in open hole section, an unexpected high-pressure zone was penetrated. The zone condition was made worse by lost circulation and a high gas reading. Two cement plugs were placed using a managed pressure cementing with pump and pull method. The first plug was set by applying surface back pressure (SBP) to maintain equivalent bottom hole pressure (BHP) between lowermost pore pressure (PP) and fracture gradient (FG) at the previous shoe. After pumping 1 m3 of cement into the annulus, pump and pull operations commenced. While performing post job circulation on the first plug, it was observed that the returned fluid density at surface was less than original mud weight, indicating the possibility of contaminant invasion from formation. After waiting for the cement to reach 500 psi compressive strength, pressure buildup was observed when annulus was shut-in, indicating an inadequate pressure seal across the cement plug Applying lessons learned from setting the first plug, new design considerations were implemented such as increasing cement volume in the annulus to 4 m3 prior to the pump and pull operation to minimize cement overlapping risk and applying SBP at BHP near FG. A contingency plan was in place to determine the appropriate SBP value to be applied whenever the pumping rate was changed. A second plug job was performed safely and flawlessly by achieving the top of cement as desired. A successful inflow test was performed with indication of no contaminant invasion nor pressure bypass around the cement plug. The rig was able to continue its next operation to sidetrack the well. This paper presents the design considerations, methodology applied, and lessons learned two managed pressure cement plugs using pump and pull method in a well bore with a narrow pore-frac window where the new techniques were implemented to enhance success of the plug job despite the complexity and risk inherent with an underbalanced operation.

A limited remaining reserve is one of the challenges commonly found in mature field development. Swamp fields in the Mahakam block is an example of mature field development which leads to a marginal operation. Delivering wells more economically is one of the key points to survive during those conditions. Rig operation with a significant daily expenditure could be a way for improvement to yield economic wells. In general, an efficient rig operation would deliver wells in a shorter duration and at a lower cost. In order to lessen the well duration, two aspects could be improved: performing co-activity operation to shorten the horizontal time (preparation) and mastering drilling practices to shorten the vertical time (drilling). In the co-activity operations aspect, various initiatives have been implemented, such as rigless operations, batch drilling, and offline or simultaneous activities. While in the drilling practices aspect, drilling parameters, bit design, connection practice, and team motivation were the areas that have been improved. This paper will elaborate further on those initiatives. Implementing massive co-activity operations and the best drilling practices have demonstrated a significant time saving of 24% for the shallow well (final depth around 1800 m) and 27% for the deep well (final depth around 4300 m) in the block. These practices have also made a new record of the fastest well completion in 2.17 days and the highest drilling ROP for 141 m/hour with drilling 2303 m in the first 24 hours. The record of most drilled length in 24 hours is the world best performance of RSS BHA as per Directional Driller Company worldwide record. As a result, the 2020 average cost of the shallow well was 2.6 MUSD while the deep well was 4.1 MUSD. Those massive co-activity operations and drilling practices have been properly executed since 2019 without any safety incident and related NPT. The positive results have helped the development project to survive in marginal conditions.

The first ever HPHT exploration well in Kalimantan was drilled by Swamp Barge Rig with narrow pressure window environment. The well was planned to be drilled using 2.9 SG mud weight to 4575 m vertical depth with 0.10 SG pressure window. Maximum predicted bottom hole temperature of the well was 186° C while the maximum expected wellhead pressure (MEWHP) reached 11,300 Psi. MPD becomes mandatory to complete the well and becomes a novel implement for swamp barge rig operation. Therefore, MPD workshop was held among the teams to ensure all personnel become familiar with the system. On other hand, the equipment configuration was set with some modifications to accommodate the operation requirement, contingency, tight stack up below rotary table and hoisting devices limitation. Rotating Control Device (RCD) was stacked up part by part on tight moon pool space. Several modifications were done properly and gave operation flexibility plus robust contingency. RCD alignment was reset periodically and natural rubbers were utilized to enhanced rubbers lifetime in high temperature condition. EKD system with Coriolis utilization was being main mitigation during drilling with limited kick margin that will allow reservoir section to be accessed. Formation pressure investigation was also performed to give additional information on formation pressure for better well assessment. SBP application on dual gradient tripping and managed pressure cementing give a means to secure the well safely and properly during high gas event with losses condition. As the result, MPD implementation enables the operator to complete HPHT exploration well on swamp barge rig project safely despite the complexity and risk of narrow formation pressure window operation.