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SMA Coating to Promote Proppant Height

IP.com Disclosure Number: IPCOM000192597D
Publication Date: 2010-Jan-25
Document File: 5 page(s) / 2M

Publishing Venue

The IP.com Prior Art Database

Abstract

Propped fracture length is often used as the primary geometric measure of a propped hydraulic fracture treatment. As the industry moves to large water frac treatments in tight rock and shale plays, there is a need to increase propped frac height. Proppant settles in the low rate environment of the open hydraulic fracture which results in less propped frac height. This paper presents theory and laboratory data indicating that the addition of surface modification agents to the proppant will yield more propped height and could provide incremental recovery and production increases.

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SMA Coating to Promote Proppant Height

Abstract

Propped fracture length is often used as the primary geometric measure of a propped hydraulic fracture treatment. As the industry moves to large water frac treatments in tight rock and shale plays, there is a need to increase propped frac height.  Proppant settles in the low rate environment of the open hydraulic fracture which results in less propped frac height.  This paper presents theory and laboratory data indicating that the addition of surface modification agents to the proppant will yield more propped height and could provide incremental recovery and production increases.

Introduction

Propped length may be defined as the distance from the wellbore to the tip of the proppant pack (measured horizontally); whereas, propped fracture height is the distance from the top of the proppant pack to the bottom of the proppant pack (measured vertically).  Fracture width is typically measured as the average horizontal distance (at the wellbore) perpendicular to the length.

More length and height are created than is propped particularly in tight rock and shale plays.  This result is a function of the low permeability reservoir yielding a high fluid efficiency even to water.  This result is also by design as water fracs typically use large volumes of water or low gel loading fluid as a pad to crack or disrupt as much rock as possible.

In

North America

, water fracs are arguably the most common type of job being performed at this time.  For example, water fracs are used across many geographic areas and reservoirs such as the Barnet Shale, Haynesville Shale, Eagle Ford Shale and the Cotton Valley Sand.  The pad stage is followed by low concentration proppant “sweeps”.  These “sweeps” alternate propped fluid and unpropped or clean fluid stages.  The sweeps are necessary to push out/over the piled up settled proppant as the proppant settles even as the treatment is in progress.

Surface modification agents (SMAs) have been used to coat proppant for many years.  Several papers1-3 have described the mechanism by which SMA materials function.  This paper will deal primarily with the vertical proppant distribution and the effect that SMA has on settling.

Proppant Settling

As proppant is pumped into an open hydraulic fracture, it settles to the bottom of the fracture.  The rate of settling is dependent upon the density of the proppant, the particle size (diameter) of the proppant, the flow rate in the fracture and the rheology of the carrier fluid.  Common treatment designs include some of the following methods to mitigate proppant settling:  1) using viscous or cross-linked fluids to suspend the proppant until the fracture closes and holds the proppant in place, 2) utilizing smaller particle size proppants (30/50 or 40/70-mesh  compared to larger 20/40 or 1...