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.

With today's oil and gas prices, the loss of well production creates a negative financial impact on operating companies, especially in an offshore environment. One of the most common reasons for production loss is the development of scales inside the production strings, blocking the flow of the reservoir fluid to the surface facilities. Barium Sulfate (BaSO4) scale is among the toughest scales to remove, whether mechanically or chemically. Alternatives to remediate this problem are often quite costly. Therefore, under this scenario, a cost-effective intervention mechanism to restore production to previous levels is imperative. One of these mechanisms is the deployment of coiled tubing intervention as it can be done while the well is still live, minimizing further loss of production. The Namorado field in Campos Basin, offshore Brazil, has approximately 60 wells, with most of them presenting deposition of BaSO4 scale throughout their production history. Historically, in this field, the deployment of a down hole motor with coiled tubing has been effective, but limited to restoring the production path's diameter only to the outer diameter of the bit. Results with deploying a down hole motor have been satisfactory. On the other hand, chemical treatments have been extremely ineffective and are, therefore, seldom deployed. This paper presents two case histories of successful Barium Sulfate scale removal from the production tubing by coiled tubing, utilizing a combination of mechanical and hydraulic tools. This process is different from the conventional method (downhole motor) as it provides faster cleanout rates and quicker production restoration. This combination is engineered through software that optimizes the velocity at which the coiled tubing string is run through the scale, as well as the configuration of the hydraulic tool with respect to the pump rate and selection of the jet angle. Introduction One of the most common reasons for production decay in oil and gas wells is scale formation inside the production tubing. In Namorado Field, Campos Basin, Brazil, the management of Barium Sulfate (BaSO4) scales is one of the most challenging objectives for the production maintenance at the field. The Namorado Field suffers, as many oilfields do, from serious scale deposition issues. In particular, the field faces a plague of hard, stubborn Barium Sulfate scale (Figure 1). Despite periodic scale inhibition treatments, many wells still suffer flow restrictions as scale deposits diminish the internal diameter of production tubing. A typical solution has been to remove and replace the production tubing, an expensive proposition because of environmental regulations treating barium sulfate-contaminated tubing as radioactive waste. Since the advent of water injection at the Namorado field, by the middle of the 1980s, laboratory tests indicated the high potential of Barium and Strontium Sulfate precipitation to occur at wells using this technique. During this time, several procedures were analyzed and implemented in order to prevent the occurrence of BaSO4 scale formation and to remove scales already in the tubing as well. In general, scales can have different sources and compositions and can be formed by different factors, such as:Increase or decrease in temperatureIncrease or decrease in pressureIncrease or decrease in salinityIncrease or decrease in pHMixing of two or more different waters