Society of Petroleum Engineers

SPE technical papers concerning proppant issues such as quality assurance, proppant crushing, fines migration, fracture conductivity, etc:

SPE 103623 - Qualifying Proppant Performance

E. R. Freeman, D. A. Anschutz, J. J. Renkes, PropTester, Inc. and David Milton-Tayler, FracTech Ltd; SPE Members

Qualifying proppant performance prior to a frac job, or simply verifying proppant performance after a frac job, can add significant value to propped fracture stimulations. Through a blend of established practices and new technology, data can be generated that will give an engineer insight into how specific proppants are designed to perform.

A primary objective is to establish representative, reliable and reproducible data via a sample collected from a large mass. American Petroleum Institute (API) Recommended Practices (RP) identifies three primary tenets: 1) representative sampling from a flowing stream, 2) standardized testing with calibrated equipment, and 3) sample retention for follow-up evaluation. Application of these practices ensures that proppant test data is valid (e.g. representative, reliable, and reproducible). Yet, these practices alone typically quantify quality but do not qualify proppant performance.

Correlation of valid well-site proppant data with published information (literature, web-sites, or fracturing simulators) enables one to identify disparities. Any differences in part may be the result of mining anomalies, manufacturing defects, transportation abuse, and/or contamination. These can directly impact the delivered performance of your chosen proppant.

Lastly, this paper introduces new patented technology that enables well-site proppant sampling and evaluation before the fracturing treatment. Having pre-frac data gives one the opportunity to make any necessary changes in fracture design and implementation to get the most from available proppant.

Case histories, onshore and offshore, support “qualifying proppant performance”.

SPE Paper 24008 - Effect of Proppant Failure and Fines Migration on Conductivity of Propped Fractures

J.L. Gidley, SPE, John L. Gidley & Assocs., Inc.; G.S. Penny, SPE, STIM-LAB, Inc.; R.R. McDaniel, SPE, Acme Resin Div. Borden

Long-term conductivity testing at realistic environment conditions has greatly improved the measurement of proppant pack permeability. However, the use of low flow rates to insure Darcy flow in such measurements has masked the total effect of failed proppant fines on proppant pack permeability. As flow rates increase, corresponding with those commonly found in the field, fines are mobilized and migrate into new positions that reduce the permeability of the proppant pack beyond that normally observed in conductivity measurements. This effect has generally been overlooked in proppant pack design.

This paper examines the extent of conductivity reduction caused by migrating proppant fines and the effect of proppant type on the extent of that reduction. The role of fines migration on the conductivity of proppant packs containing two different types of proppants, where the more capable proppant is used near the wellbore, is also evaluated. Representative commercially available proppants, including sand, resin-coated sand, and low density ceramics are included in the study.

SPE Paper 7007 - Formation Fines and Factors Controlling Their Movement in Porous Media

T.W. Muecke, SPE-AIME, Exxon Production Research Co.

Microscopic observations of fine-particle movement in micromodels of porous media have shown that transport of these particles by fluids moving through pores is controlled by several factors. Besides mechanical bridging at pore restrictions, fines movement also is influenced strongly by particle wettability and the relative amounts of fluids flowing through the pores when two or more immiscible fluids are present.

SPE Paper 37489 - Understanding Proppant Closure Stress

S.K. Schubarth, SPE, Halliburton Energy Services, S.L. Cobb, SPE, Carbo Ceramics Inc.; R.G. Jeffrey, SPE, CSIRO Petroleum

The effect of closure stress on fracture conductivity has been well documented by laboratory measurement. Common industry practice for estimating closure stress on proppant in the field is to subtract flowing bottomhole pressure from the estimated in-situ stress of the pay interval fractured. This paper proposes that the closure stress on proppant in a fracture can be significantly higher than common estimations due to the influence of the bounding layers and the elastic response of the formation acting on the proppant. In this paper we will review past literature on fracture propagation, fracture conductivity and proppant placement and demonstrate the impact that increased proppant stress due to bounding layers can have on fracture conductivity and ultimately production.

SPE Paper 90562 - Investigating How Proppant Packs Change Under Stress

Stephen Schubarth, Schubarth Inc. and David Milton-Taylor, FracTech Ltd.

Proppant conductivity is an important design criterion in hydraulic fracturing treatments. Knowing how different proppants behave under changing stress conditions is important to fracture stimulation success. Conductivity and non-Darcy flow effects has been laboratory measured for all ceramic proppants. Unfortunately, almost all laboratory measurements are performed with an increasing stress and cyclic stress behavior is not observed. Often, in the production of oil and gas wells, shut-in periods occur and pressure in the wellbore and proppant pack increases causing stress to be relieved on the pack. When production begins again, stress is increased on the pack. This is stress cycling and past publications1 have noted that stress cycling can cause a reduction in proppant pack conductivity.

SPE Paper 16912 - Flow Response of Propped Fracture to Repeated Production Cycles

C.M. Kim and J.R. Willingham, BJ-Titan Services Co

Once a reservoir is hydraulically fractured, the fracture may experience several repeated production/shut-in cycles. Evidence of reduced rate of recovery as wells are placed back on production, has been noted in gas wells that have been exposed to this type of cycling. As the cycling process is repeated, the propped fracture undergoes the ups and downs of closure stress, resulting in a gradual reduction in fracture conductivity.

SPE Paper 84304 - Is Ottawa Still Evolving? API Specifications and Conductivity in 2003

Chris J. Stephenson, Allan R. Rickards and Harold D. Brannon, SPE Members, BJ Services Company

Proppant mesh size is arguably the most important characteristic for controlling and describing the quality of a particular propping material. More importantly the mesh size relates to the permeability performance of the proppant. For many years now, a series of American Petroleum Institute Recommended Practices have existed for testing the quality of the numerous proppants available. Along with testing procedures, these documents contain suggested typical proppant sizes, such as 20/40 mesh, and the size specifications they should meet both at the source and at the point of application. In addition to other size criteria, it has long been accepted that if a batch of proppant has at least 90% of its mass between the designating mesh sizes, it passes an acceptable quality control target. However, it is possible to have two samples of 20/40 proppant that are both 90% in-size but could, for example, have a two-fold difference in permeability due to differences in distribution. In this case would the median diameter be a more informative description of the proppant size?