The Long-Term Production Performance of Deep HPHT Gas Condensate Fields Developed Using Formate Brines

Abstract

Formate brines have been in use since 1995 as non-damaging drill-in and completion fluids for deep HPHT gas condensate field developments. The number of HPHT fields developed using formate brines now totals more than 40, and includes some of the deepest, hottest and highly-pressured reservoirs in the North Sea. The well completions have been both open-hole and cased-hole.An expectation from using formate brines as reservoir drill-in and completion fluids is that they will cause minimal damage to the reservoir and help wells to deliver their full productive potential over the life-time of the field. The validity of this expectation has been tested by examining the long-term hydrocarbon production profiles of eight HPHT gas condensate fields in the North Sea where only formate brines have been used as the well completion fluids. In five of these fields the wells were drilled with oil-based muds and completed by perforating in cased hole with high-density formate brines. In another two of the fields the wells were drilled with formate brines and completed with screens entirely in open hole using the same brines.The last of the eight fields was drilled with formate brine and the wells were then completed with same fluid in either open hole or cased hole.The results of the production analysis provide a unique insight into the impact of a single type of specialist drill-in and completion fluid on the rate of recovery of hydrocarbon reserves from deeply-buried reservoirs in the North Sea.

High pressure phase equilibrium of ternary and multicomponent alkane mixtures in the temperature range from (283 to 473) K

“…In the preparation of a sample mixture, the sample side of the high pressure cylinder was first evacuated by using a vacuum pump Edwards E2M1.5 for at least 3600 s. The liquid compounds of the mixture were then added to the sample side of the high pressure cylinder through a burette with a standard uncertainty of 0.01 cm 3 . In the case of the ternary mixtures a known volume of n-decane or n-dodecade was added by using the burette.…”

“…Due to the declining conventional oil and gas resources, oil companies tend to explore and produce from more difficult resources such as tight formations, heavy oil, and deeper reservoirs often at high pressure and high temperature (HPHT) conditions [1,2]. For offshore HPHT fields [3], the exploration and production becomes even more costly and risky, requiring a more accurate description of the production and a more careful design. In order to design and forecast the production of these HPHT reservoirs, an accurate description of the relevant phase equilibrium and…”

Formate Drilling and Completion Fluids: Evaluation of Potential Well-Productivity Impact, Valemon

“…Formate brines have been used over a number of years as drilling-and-completion fluids for HP/HT fields (Howard 1995;Bungert et al 2000;Saasen 2002;Simpson et al 2005;Oswald et al 2006;Berg et al 2009;Qureshi et al 2008;Downs 2011;Olsvik et al 2013). Olsvik et al (2013) summarized the results from eight HP/HT fields in which cesium formate was used as the completion fluid in conjunction with a cesium-formate drilling fluid or oil-based mud.…”

“…Olsvik et al (2013) summarized the results from eight HP/HT fields in which cesium formate was used as the completion fluid in conjunction with a cesium-formate drilling fluid or oil-based mud. These results were used to validate the claim that formate brines could cause minimal formation damage.…”

“…In addition, the formation of precipitates because of the interaction of drilling-and-completion-fluid losses with formation water could be avoided because formate does not contain any divalent cations that can react with bicarbonate and sulfate. The concluding remark of Olsvik et al (2013), "…deep HTHP gas wells completed using cesium formate brine in open hole with stand-alone sand screens seem to be robust, durable and productive," has been demonstrated to be valid for wells completed and put on production after a matter of weeks. To demonstrate the absence of any detrimental effects with long-term contact of formate and the near wellbore, CFD modeling was performed to assess the effect of gravity sinkage vs. formate contact with the near wellbore.…”