Novel Single Trip Horizontal Gravel Pack and Selective Stimulation System Improves Injectivity in Deepwater Wells

Abstract

Conventional horizontal gravel pack completions typically require multiple trips. Disadvantages of the conventional system may include the loss of rig time due to multiple trips and repeated rig-up / rig-down of pumping equipment, formation damage due to completion fluid losses and fluid loss pills, and incomplete filtercake cleanup across the entire gravel packed interval. A novel single trip horizontal gravel pack and selective stimulation (SHGPSS) system has been developed and implemented. This system allows the gravel pack assembly to be installed, the gravel pack to be pumped, and selective stimulation of the entire packed interval to be performed - all in a single trip. The benefits of the SHGPSS system include valuable rig-time savings and, efficient mechanical diversion of the stimulation fluid. This paper outlines the first applications of the SHGPSS system to successfully complete five deepwater horizontal injection wells in the Campos Basin, offshore Brazil. Hydrostatic pressure was maintained on the formation during all treatment phases, thus preventing any underbalance that could lift the filtercake off the formation and cause undesirable fluid losses. After gravel packing, a secondary ball was dropped opening a bypass area and converting the gravel pack tool to a selective stimulation tool. The system then provided the ability to perform a filter cake cleanup and stimulation by selectively treating the horizontal interval 40 ft to 80 ft at the time, depending on the screen joint length. Economic considerations along with completion efficiencies are especially important on deepwater, subsea completions. The novel SHGPSS system can reduce rig-time generating significant cost savings. Exceptional mechanical diversion of the stimulation fluid allows effective filtercake and formation damage removal yielding efficient completions. Case history information on five subsea, offshore Brazil, deepwater wells will further detail the optimized completions accomplished utilizing the SHGPSS technology. Introduction Most oil and gas reserves in Campos Basin (Figure 1) are located in deepwater (300m - 1000m) and ultra-deepwater (greater than 1000m). Economics dictate field development and planning is the key for successful return on investment. Completion systems that can minimize rig time and future interventions are particularly important for deepwater and ultra-deepwater environments. The reservoirs of the Marlim and Marlim Sul fields located in Campos Basin are described as sandstone without water influx and require substantial water injection for pressure maintenance. Historical experience has verified that the reservoirs are unconsolidated and require sand control for both injectors and producers1. Economic development of deepwater projects demands that a minimum number of wells be drilled and still effectively drain the reservoir2. The horizontal completions can be producers or water injection wells, depending on the needs of a specific location. A major concern for these completions is to minimize formation damage caused by drilling mud left in the hole. Prior to running the completion tools, drilling fluids are circulated out of the wellbore at high rates in order to leave a thin filtercake at the formation interface. The filter cake is necessary to maintain wellbore stability and minimize fluid losses during gravel packing operations in order to achieve a successful gravel pack of the entire interval. However, fracture gradients can limit flow rates necessary to lift drilling fluids out of the wellbore. The result is high skins due to mud trapped between the gravel pack and formation, requiring well intervention. This is particularly true for injectors where no flowback of produced hydrocarbons clean up the skin damage caused by drilling the well. The SHGPSS system was developed for horizontal open hole injectors as well as producers by allowing for gravel packing and selective stimulation in a single trip as well as fluid loss control.

The 200th Horizontal Openhole Gravel-Packing Operation in Campos Basin: A Milestone in the History of Petrobras Completion Practices in Ultradeep Waters

“…Its use has enhanced the efficiency of our acid treatments. 9 Pereira et al also describe the development of a tailored coiled-tubingconveyed acidizing tool for post-gravel packing applications. 10 Another matter of concern is the excessive corrosion of the screens that may take place in acidizing operations.…”

Deepwater Horizontal Openhole Gravel Packing in Marlim Sul Field, Campos Basin, Brazil—Completion Project Learning Curve and Optimization

“…This tool system allows set-down weight to be applied in both squeeze and circulating positions to eliminate problems associated with tubing movement during well treatment. The tool system design is simple, with no extra collets or indicating subs required, and offers mechanical indications of all positions and tool movements (Vilela et al 2003;Farias et al 2004). …”

“…Producer wells were flowed back. The development of the HST (one trip) gravel-pack tool abled to be converted to an acidizing tool, saved rig time and increased the efficiency removing filter cake because of the ability to mechanically divert the treatment it (Vilela et al 2003;Germino et al 2004).…”