Profiling the Production Performance of Five HPHT Gas Condensate WellsDrilled and Completed with High-Density Cesium Formate Fluids in theBrent Group Formations of the Kvitebjorn Field

摘要

This paper provides insights into the long-term production performance of a set of five HPHT wells drilledand completed with SG 2.0 cesium formate fluids across the entire sequence of gas-filled Brent Groupreservoir formations of the Kvitebjorn field during the period 2004/5.Three of the wells were completed in open hole with screens and the other two with cemented andperforated liners.All of the wells cleaned up naturally during production start-up.Well logs run in the firstseries of wells drilled and completed with cesium formate fluids provided enhanced reservoir informationindicating improved reservoir quality which translated into a 33% increase in the Hydrocarbon Pore Factor(HCPF).After a year of production from these wells a new updated reservoir evaluation,factoring in theimproved reservoir quality and more reservoir volume,increased the overall Kvitebjorn recoverable gasreserves by 50% to 79.97 GSm~3 of gas and 30.13 million Sm~3 of condensate.As a result of this evaluationthe expected recoverable reserves for the first five production wells drilled in 2004/5 rose from 32.7 GSm3to 48.3 GSm3 for gas and from 12.3 MSm3 to 14.8 MSm3 for condensate.Apparent reductions in well productivity indices(PI)of 20-80% were measured in the first 5-7 yearsof production.The PI reductions could have resulted from a combination of scaling,condensate banking,reservoir compaction or even problems with the PI estimations.One of the wells with a liner completion wasre-perforated twice(in 2012 and 2015)and another well with a screen completion was perforated throughblocked screens in 2015,but the remaining three wells have continued to produce without intervention for14 years.The cumulative gas production from the five wells up to October 2018 stood at 60.1 GSm3,whichis already 24 % higher than the mean total recoverable reserves predicted in the 2006 reserves evaluation andalmost double the figure anticipated in the original 2004 field development plan.The cumulative condensateproduction over the same time stood at 20.4 MSm3,which is 38 % higher than the mean total recoverablereserves predicted in the 2006 reserves evaluation and almost double the figure anticipated in the original2004 field development plan.In laboratory formation damage tests conducted at 150°C the oil permeability of a Kvitebjorn reservoircore plug flooded with a sample of the cesium formate drilling fluid recovered from the field after use in all five wells was reduced by 65% from 29 mD to 10.2 mD.This very valuable test may now allow aretrospective evaluation of the predictive value of that particular laboratory-based return permeability testmethod used to assess the formation compatibility of that formate fluid twelve years ago.