Flowback and Well Testing Operational Learnings During an Early Production Stage in a Vaca Muerta Field

Abstract

La Calera is an unconventional wet gas field located close to Añelo city in Neuquén province. There are currently 30 horizontal wells in production from Vaca Muerta formation, drilled at three different landings zones, gathered in 3-well pads. The wells are first opened using testing facilities in order to evaluate their productivity, as well as to prevent liquids and sand from reaching plant facilities. This paper describes the lessons learned after the first wells flowback, the different events that had to be sorted (sand blockage, erosion, hydrates, etc.) and the operational workflows that were created in order to manage sand and fluids production from the wells. Testing facilities consist primarily of two gas-oil-water 3-phase separators, a flash medium pressure separator, and a last separation stage used to stabilize the condensate in a flash-tank. There is also one desander per well, and several tanks in order to collect liquids in the pad location. This equipment is necessary because the wells are currently flowing to Early Production Facilities (EPF) that do not allow liquid slugs nor high sand production. Gas, condensate and water rates, well head pressures and sand production are measured in every well hourly. A first choke management strategy for each well is proposed and their productivities are estimated using previous wells information regarding productivity, ratios, sand production, and a choke correlation. The first unconventional well was opened in 2019. Three years after and using flowback lessons learned, several testing configurations were changed, liquids heaters removed, sand equipment changed, line diameters modified, chemical injection points and doses adjusted, and different operational criteria established. A sand management workflow was developed and is currently being applied during pads openings. During the first clean up period that usually lasts from 3 to 4 months, the initial choke management plan is constantly being modified due to operational challenges such as hydrates formation, excessive sand or liquid production, and operational problems like valve failures or facilities limitations, all of which will be described in this paper.