An offshore operating company used the VERSAPRO™ invert-emulsion reservoir drill-in fluid system with the VERSA-OUT XT™ OBM delayed aqueous filtercake breakers in four high-temperature wells. No losses were observed during spotting of the breaker. Production rates surpassed expectations.
The operator planned to improve formation productivity while reducing sand production for a joint development area between Malaysia and Thailand.
The shallow water wells drilled were part of the development project in a sandstone formation with bottomhole temperatures reaching up to 285 degF with a 11.1 lbm/galUS of VERSAPRO invert-emulsion reservoir drill-in fluid system. Due to the different targets aimed in the development phase, the wells had trajectories varying from slight deviation to horizontal.
The typical completion design was a cased hole perf operation for this customer in this area. In order to enhance production, the completion style was changed to an openhole completion, thus requiring a fluid design change that would not cause formation damage.
The fluid design challenge was related to achieving high density of the system without the use of barite or with a calcium chloride internal phase. One way to achieve a barite-free system is to reduce the oil/water ratio, change the brine of the internal phase, however, this changes the rheological profile, which may potentially affect ECD. For this client, the use of CaCl2 as the internal phase instead of CaBr2 was driven by economics. Therefore, when using the CaCl2 internal phase, an increased concentration of calcium carbonate is required to achieve the desired density.
There was another challenge identified in terms of breaker delay due to the bottomhole temperature of 285 degF. At high temperatures conventional breaker systems may not deliver the required delay to pull of hole to close the isolation valve before incurring losses. Such losses could create a hotspot, causing sand production and incomplete dissolution of the filtercake affecting production.
The operator agreed to the change in methodology by implementing VERSAPRO system and VERSA-OUT XT breaker from the MUDSOLV NG™ integrated filtercake removal service.
The VERSAPRO system was engineered to deliver a stable rheological profile even while using a high calcium carbonate loading. The VERSA-OUT XT breaker was engineered to address the delay time to efficiently spot the breaker at the optimal bottomhole temperature. A delay of more than 6 h was observed with no losses.
The drilling to completion fluids design was used on four wells; they delivered higher than expected production rates.
