Efficient Offshore Scale Removal Without a Rig: Planning, Logistics, and Execution

Abstract

Although the oil industry seeks to increase the worldwide production of hydrocarbons, various well and reservoir problems can severely reduce oil and gas production from individual wells, leading to the requirement for intervention. For example, in mature fields offshore Brazil, production platforms with minimal open work space and without workover rigs have been a challenge for restoring production in wells with serious scaling problems. The scale build-up reduces production, month by month, until a rig has to be mobilized to replace the production string. Trying to recover production efficiently, service and operating companies have been presenting solutions that circumvent the practical limitations of these locations. In the last three years, an operator's engineering department has worked with service company engineers to develop the means to rig up a 1–3/4-in., 4500-m-long coiled tubing string in a work area of 234 sq. meters and with a crane with a 12-ton maximum capacity. This cooperation allowed intervention in wells on rigless platforms, reducing working time, environmental impacts and costs. These interventions helped to increase oil production from Field A in the Campos Basin and gas production from Field B in the Santos Basin, currently the most important gas field offshore Brazil. Both fields suffer from severe scale deposition -- barium sulfate in Field A and calcium carbonate in field B -- which builds up in the production string and effectively reduces the internal diameter, consequently reducing production. The new successful interventions in these fields using rigless coiled tubing and scale removal techniques enhanced the hydrocarbon production from these fields. In Field A (oil production), interventions were performed in seven (7) wells, providing around a 40% increase in production. In Field B (gas production), interventions were performed in five (5) wells, providing a production increase of around 27% per day. This paper details the planning, logistics and techniques used to successfully meet both challenges. The same solutions would apply in other fields around the world where platform space and scarcity of rigs limit an operator's ability to remediate scale or other wellbore problems that constrain hydrocarbon production. Introduction Market demand has sparked renewed interest in increasing oil and gas production from mature wells in Brazil for the last three years. The result has been an expansion in stimulation techniques using coiled tubing as a thru-tubing tool. Mature production wells, offshore Brazil, are located in both carbonate and sandstone reservoirs. Most of them are naturally depleted and heavy oil / high basic sediment & water (BSW) producers, with a carbonate, sulfate and paraffin scale deposition history. The choice for Coiled Tubing interventions seems to be obvious due to the speed of operation and almost immediate increase in incremental production without production interruption during operations. However, the barriers to project viability included crane lifting capacity, which hindered the ability to place the working reel onboard existing platforms, and the restricted working area available to execute the intervention (Fig.1) in wells ranging from 3500 to 5770 m total depth. Using the correct approach and planning procedures, and involving both service company and operator technical specialists, a new and innovative technique for rigging up and intervention was arrived at to overcome the existing obstacles.

An experimental approach to the descaling of production tubing using high pressure flat fan nozzles

“…Many inefficient and unsafe scale removal techniques like the destructive mechanical method (that is, with that is, explosives) (Alabdulmohsin et al, 2016), the use of aggressive chemical solutions such as like HCl (Hamdy et al, 2014;Vazirian et al, 2016), rig work over to replace the tubing and even differing of production haves unsuccessfully been tried in the past (Guimaraes et al, 2008). Although recently, the mechanical high-pressure water jetting techniques has been widely accepted by the multinational (Bajammal et al, 2013), despite facing back pressure challenges (cavitation).…”