Abstract
Managed Pressure Drilling is an adaptive drilling technique used to precisely assess the formation pressure limits and manage the annular pressure profile accordingly. MPD uses a lighter mud density that with assistance of surface backpressure maintain the overbalance condition, and the dynamic adjustment of this surface pressure allows to maintain Constant Bottomhole Pressure (CBHP) in both dynamic and static conditions. Generally, MPD system reduces the extra overbalanced pressure applied on a formation while drilling conventionally
Recently, the operator utilized Managed Pressure Drilling (MPD) Constant bottom hole pressure (CBHP) technique to drill a challenging HPHT gas well successfully through an exploration field. The case study field elaborates challenges of uncertain formation pressure, narrow pore pressure-fracture pressure window and high background gas readings leading to extreme well complications. These challenges were counteracted with the implementation of Managed pressure drilling MPD technology, enabling to drill a well without any complications.
To coupe with the complications including high temperature, narrow mud window & CO2 influx, MPD technology was called to be utilized in the challenging exploration field. With the implementation of MPD in this exploration drilling campaign, the case study well proved to optimize the overall drilling process, hence proving an answer to the previous problems in the field. The subject well was the first well to reach this depth. As a starting point, the actual bottom hole pressure limitations were established by performing MPD pore pressure tests, due to the lack of data as the only other option was to rely on geo-mechanics interpretations which is not very accurate, considering the case study specifically. Being it an exploration field, the bottom hole conditions were inconsistent and uncertain. The fully automatic MPD system enabled real-time evaluation and instant adjustment of the bottom-hole formation pressure changes, throughout the drilling process. The precise and instant control of bottom-hole pressure was the key factor of the overall success, hence mitigating any well complications, which previously costed weeks of rig days and associated oil based mud costs during losses. Since MPD technique evaluates & optimizes the required mud weight, hence saving the unnecessary overbalance on the well which had been the cause of several problems previously like losses, differential sticking and ballooning. Furthermore, for these critical narrow window wells, there was a need of a fool proof gain/loss monitoring system to stay top of the game all times. The sophisticated early kick/loss detection feature of the MPD system added value to the operation, which was independent of the conventional rig mud pit transfers and mixing which usually trigger false gain/loss alarms.
The narrow drilling window was exacerbated by the increase in annulus frictional losses for these extended wells. The approach of ‘Prevention is always better than cure’ was adopted by the operator, since MPD prevents/mitigates a lot of hazards before they happen. This publication summarizes the details of how the MPD CBHP technique, early kick detection system & instant control system made it possible to efficiently and successfully execute the drilling process safely. It was proved that real time monitoring, and instant reactions are necessary to be able to adjust the BHP to keep the well under control throughout the drilling and post drilling operations like reaming trip in these types of high gas bearing formations.
Hence MPD enabled the drilling of complex geological and weak fracture strength formations without any NPT for well control situations with the few value-added benefits like improved ROP, extending the total depth by 1300 ft additional to the initial plan achieving the deepest TVD (true vertical depth) drilled in the field.
WELL-SEISMIC INTEGRATION TO PORE PRESSURE PREDICTION USING MULTIVARIATE GEOSTATISTICS: A CASE STUDY IN A BRAZILIAN EQUATORIAL MARGIN BASIN