Engineered fluid system reduces plug & abandonment costs
We’re always very passionate about talking about muds - our clients see that everyday. Some fluid discussions are simple, and others are more complicated. A recent Gas Well Program we worked on was a challenging one, requiring a sophisticated engineered mud program. We thought you might like to know about some of the various projects we are involved with, and some of the higher level technical drill fluid systems that are a part of what we do.
Blick and MI SWACO were recently contacted by a customer to provide high density brines, cleaning and perforating fluids, and cement spacers, for a series of plug and abandonment (P&A) operations.
When a well is to be closed permanently; usually after either logs determine there is insufficient hydrocarbon potential, or after production operations have drained the reservoir - cement plugs are placed within the wellbore. Whilst plugging operations can differ depending on the regulatory body; typically cement plugs are placed across open hydrocarbon-bearing formations, across all casing shoes, freshwater aquifers, and other areas near the surface, including the top 6m to 15m of the wellbore.
As part of the initial preparation for a P&A well, a high-density drilling fluid is circulated in the wellbore. These fluids are typically clear brines formulated with chlorides, bromides and formates, with the key driver being well control (ensuring no formation fluids/gas comes to surface).
MI SWACO Drilling Fluid Specialist, Andrew Bilton, worked with the client - to design a fluid program for the five HTHP (high temp high pressure) well campaign proposing fluids, blended to specifications based on bottom hole pressures and service temperatures.
Required densities of the ‘kill’ fluids ranged from 9.04ppg – 12.61ppg and temperatures up to ±204˚C. Fluid densities up to 9.8ppg can be achieved easily and cost effectively using Sodium Chloride (NaCl), but weighting up over this requires switching to heavier brines. Calcium Chloride (CaCl₂) to 11.6ppg, Sodium Bromide to 12.7ppg or a Calcium Bromide (CaBr₂) or formates >12.7. Heavier clear brines (especially formates) are very expensive, and are often leased rather than purchased. The recovered fluid is returned to the supplier, filtered and leased out for other operations.
After considering the operational parameters, a kill fluid was blended using a combination of DUO-VIS suspension agent, PTS-200 polymer temperature extender, SAFE-SCAV (H₂S scavenger) and M-I BAR (barium sulphate) weighting agent. Using this suite of products, the client was able to weight up initially to the maximum 9.8ppg with NaCl and then make M-I BAR additions as required to achieve the required density.
Using this engineered fluid solution as a substitute for the Sodium Bromide, it is estimated that the client was able to reduce their costs on the 12.61ppg well by ~90% and on the total campaign by ~60%.
Author: Andrew Bilton Drilling Fluid Specialist M-I SWACO
Blick has been a supplier to the drilling industry in Australasia for 50 years. Blick and MI SWACO work as a partnership - for water based drilling fluids across Australia, New Zealand and the Pacific. Having great products is important, but what makes an even bigger impact is working with great partners. Blick and MI SWACO focus on helping you; to design the best solution to fit your circumstances, and we have the people, and ability, to help you deliver on site.
If you’re looking at optimising your drilling performance and reducing costs through engineered fluid solutions, contact us today for an engineered solution. Our Australia team is available on +61 3 9068 5688 and New Zealand on +64 7 849 2366.
