Scale Inhibitor Squeeze Treatments Deployed From an FPSO in a Deepwater, Subsea Fields in the Campos Basin

Abstract

This paper describes field experience and lessons learned from scale control operations in a deepwater subsea development in the Campos Basin, Brazil; specifically, from bullheading scaleinhibitor squeezes from the FPSO host, along the production flowlines, into four low-watercut, horizontal subsea wells, completed with sand control.The relatively small number of high-cost, highly productive wells, coupled with a very high barium-sulfate scaling tendency upon breakthrough of injection water, meant that not only was effective scale management critical to achieve high hydrocarbon recovery, but even wells at low water cuts were deemed to be at sufficient risk to require squeeze application.Use of conventional, water based squeezes have been known to cause significant damage to productivity in low-watercut wells, including those showing a fines-migration tendency, as was the case here. Hence, on the basis of risk mitigation, supported by an extensive program of laboratory testing, it was decided that for the initial treatments, only the mainflush would be water based, with a mutual-solvent preflush and marine-diesel overflush.Other key challenges associated with treating from the host included the remote location of the wells, the potential to form hydrates, the cleanliness of the lines along which the treatment would pass, the achievement of effective placement over a long producing interval, as well as the need to deploy the chemical package via a support vessel adjacent to the FPSO. All had to be managed because of the high cost and low availability of a deepwater rig that could deploy the treatments directly to the subsea wellheads. This paper will explore in detail the issues associated with inhibitor-squeeze deployment in deepwater, subsea fields, many of which are currently being developed in the Campos basin, Gulf of Mexico, and West Africa, and are a good example of best-practice sharing from another oil basin.Downhole Scale Surveillance. Production Surveillance. Continuous monitoring of well performance is carried out using pressure and temperature gauges, both downhole and at the subsea wellheads, thus allowing productivity indices, pressure drops across the tubing, and instantaneous changes in gross rates, all to be effectively monitored. These are supplemented by regular well tests that can assist in deconvoluting changes in productivity because of formation damage from that because of changes in gas lift rates, reservoir pressure, wettability, reservoir saturations etc.

Evaluation of Barium Sulfate Scale Inhibition Using Relative Permeability Modifier Polymers as Adsorption Enhancer for Mature Offshore Well Treatments in Campos Basin, Brazil

“…In addition, many fields in the basin present problems associated with inorganic scale, causing further reduction of the wells productivity. Among different inorganic scales, barium sulfate is one of the most recurrent in the Campos basin. , …”