Screenless sand control completions provide a cost-effective means of completing wells in the Gulf of Mexico by eliminating the need to have a rig on location. To date, six screenless completions have been performed for a major operator in the Gulf of Mexico. Each of the six treatments provided significant cost savings, as well as excellent return on investment for the operator.
Screenless completions are an integrated solution that involve many field-proven technologies such as reservoir characterization, perforating, coiled-tubing intervention, matrix acidizing, resin consolidation, optimized fracturing with proppant flowback control, and fines migration prevention. The proper candidate selection, treatment design, treatment execution, production management and co-ordination of all services are essential to the success of the screenless completion.
In this paper, the common sequence of events for a screenless completion is presented as well as the key technologies involved, from perforating to production. Each of the six case histories are examined in detail and will show that screenless completions provide effective through-tubing sand control in a variety of well conditions. Screenless completions have been proven effective in reservoirs from 10 to 60 ft in thickness, at depths from 4,000 to 10,500-ft true vertical depth, in casings from 3–1/2 to 9–5/8-in. and in oil and gas reservoirs at rates of up to 600 BOPD, 1750 BFPD or 3.5 MMSCFD and in wells deviated as high as 42o. The technique can also be applied in different wellbore configurations to target pay behind casing, and also zones that are located behind both tubing and casing.
A sand control completion is required when there is a probability of formation sand production during the life of a well. The key factors that dictate the need for sand control are rock properties and well dynamics such as Unconfined Compressive Strength (UCS), Young's Modulus, porosity, production rate, and drawdown. Sand production can lead to facility upsets, erosion of tubulars, production decline, and in extreme cases, loss of the well. Currently, sand control is the primary completion technique in offshore environments such as the Gulf of Mexico, West Africa, Brazil, Trinidad, and South East Asia. However, it is predicted that as fields onshore deplete, a new sand control market will emerge.
The majority of cased-hole sand control completions are installed in new wells. The most common method is to install a filtering media, i.e., screens and sized gravel or proppant to exclude formation sand and fines from entering the wellbore. Depending on vicinity-to-water, reserves and economics, there are three gravel-placement options. In the order of low-to-high skin, the options are: Frac-Pack, High Rate Water Pack (HRWP), and Gravel-pack 1–3. Each of these options involves downhole hardware that is primarily conveyed by a rig. However, there are instances when sand control is performed through-tubing (rigless intervention) for workover or secondary pay sands 4&5. Prior to screenless completions, sand control options for these secondary targets have been limited.
A screenless completion eliminates the need for screen to prevent sand failure. In addition it can be done rigless. The technique consists of the following key steps:
Optimum perforation phasing and size
Tip screen out fracturing using proppant flowback control such as resin-coated proppants and fibers.