Tail-In Proppant and its Importance in Channel Fracturing Technique

Abstract

The channel fracturing technique achieves heterogeneous proppant placement by pumping pulses of proppant laden slurry and clean fluid in alternating sequence. Successful creation of proppant banks in the fracture provides stable channels of infinite conductivity which reduces pressure drop across the hydraulic fracture and enhances production. To date, more than 15,000 fracturing jobs have been successfully placed in various types of formation and completions using the heterogeneous proppant placement technique. The mechanics of delivering the treatment involves pumping pulses of alternating clean and dirty pulses of fluid with fibers that keeps the proppant in suspension. This is then followed by a continuous proppant "tail-in" stage towards the end of the job before the flush stage. This tail-in ensures continuous proppant bank at the near wellbore region to ascertain good connectivity between wellbore and the channel spaces created during the treatment. To understand importance and requirement of tail-in, simulations and field execution of jobs with or without tail-in in channel fracturing treatment have been done. Furthermore, a bigger sized unconventional rod-shaped proppants have been also used towards end of the channel fracturing treatments. The unconventional proppants not only helped on such treatments to minimize pressure drop across the tail-in but also helped to reduce proppant flowback in softer formations. The impact of tail-in on pressure drop and production rates in different formations have been consolidated in this study which provides proppant selection criteria for channel fracturing tail-in stage. Simulation results in shale and sandstone reservoirs and the field treatment case histories comparing the production results for wells completed with and without tail-in in channel fracturing treatment are presented.

Improving Hydraulic Fracturing Productivity in Khalda Oil Fields (Western Desert -Egypt)

“…It was found that the fracture conductivity of the channel fracture [745,294 Md. Ft] is much higher than that of the conventional one [3,244 Md. Ft].…”

“…A proppant-laden pulse will create a pillar and a proppant-free pulse will create channels that are supported by pillars of proppants created during fracturing. 2, 3 To make sure that the pillars will keep channels open at reservoir conditions with fluid flow through the channels, fibrous materials are added at engineered concentrations and used to :(a) minimize the dispersion of the proppant-laden pulses as they travel throughout the surface equipment and lines, along the wellbore and within the fracture; (b) enhance the proppant carrying capacity, thus boosting the proppant to transport farther within the formation; (c) mitigate proppant settling within the fracture to maintain the heterogeneous placement of proppant and deliver better vertical coverage of the fracture; 2 and (d) help to consolidate pillar structure before fractures are closed. 4 Another way to create stable and highly conductive channels within a propped fracture is by blending proppant coated with an agglomerating agent, such as a nonhardening resin, in a gel fracture fluid instead of fibers.…”

“…The resin coats the proppant with a thin, tacky, non-hardening coating that dramatically increases inter grain friction and holds the proppant aggregates together as a proppant-aggregate bed thereby reducing proppant flowback, and enhances the fracture conductivity. 5 Cluster Perforation, that means the zone isn't fully perforated, 3 is preferred to separate proppant pulse into smaller slugs, so that proppant packs are distributed greater evenly and regularly along the wellbore which improves the fracture conductivity. This way, hydrocarbons can flow through the channels separating the proppant pillars rather than flowing through the proppant pack itself as in conventional fractures.…”

Experimental Investigation on the Fracture Conductivity Behavior of Quartz Sand and Ceramic Mixed Proppants

“…Many scholars have suggested replacing the traditional single proppant design with the combined proppants, which may be segregated by tail-in, evenly blended, or blended with dominant concentrations of one particular size. − In the study of segmental by tail-in, the conductivity variation characteristics of different proppant types, sizes, and mass ratios have been investigated. , And a relevant empirical model based on the experimental results has also been proposed . In the study of the mixed proppant, some research on the conductivity of a mixed proppant pack with different sizes and types has produced some interesting findings.…”