Proppants properties

Relatively small quantities of a bacterial cellulose (0.60 to 1.8 g/liter) in hydraulic fracturing fluids enhance their rheologic properties [1425]. Proppant suspension is enhanced and friction loss through well casings is reduced. 

This quality is often used when determining rheological properties of foams when proppant is present (6) (Figure 2). 

Texture. Foam texture is an important parameter that affects the rheology of the foam fluid. Texture of a foam is a means of classifying a foam according to its bubble size, shape, and distribution within the foam matrix. Texture is a description of the manner in which the gas bubbles are distributed throughout the liquid phase of the foam. This property not only influences the foam s rheology but also its fluid loss, proppant transport, and cleanup properties. The texture of a foam is a qualitative rather than a quantitative value, and therefore a number cannot be used to describe it a physical description will be used. Factors that effect the texture of foams are quality, pressure, foam generating technique, and chemical composition. 

The only variable that can be measured directly is the surface treating pressure (STP). The hydrostatic head (HH) and friction pressures (FP) must be calculated from two measured parameters, fluid injection rate and proppant concentration, and the perforation friction pressure drop (PFP) can be determined from the physical properties of the fluid. 

We discuss the suspensions used in well stimulation and hydraulic fracturing processes. The following sections pertain to various types of suspensions used in well stimulation and fracturing processes, their rheological characterization and hydraulic properties, behavior of suspensions in horizontal wells, a state-of-the-art review of proppant settling velocity and proppant transport in the fracture, presently available measurement techniques for suspensions and their merits, and, finally, a summary and conclusions on the use of suspensions in well stimulation. Future industry needs for better understanding of the complex behavior of suspensions are also mentioned in this section. 

Hydraulic properties, that is, friction-loss calculations of proppant-laden fluids or slurries, are very important not only in the design of any hydraulic fracturing treatment but also in real-time monitoring of fracturing treatments. Recent advances (27, 28) in real-time fracture analysis have necessitated an accurate knowledge of bottomhole treating pressure (BHTP). To estimate BHTP, an accurate prediction of friction pressures of fluids in the flow conduit is required. It is possible to obtain the BHTP from the surface pressure with the following equation ... 

The materials commonly used as proppants can be grouped into three main categories, listed in Table 10.25. The first proppant material used was rounded silica sand mined from glacial deposits. This material was initially selected owing to both its wide availability near production wells and its low cost, but since the early days several other industrial materials have been selected and used as proppants, and today we observe the increased use of synthetic materials, especially sintered and fused ceramics. The main impetus in focusing on ceramics was driven by the fact that ceramic materials offer suitable properties for use in modern deep wells today. 

TaMe 10.24. Critical properties for proppants Critical properties Description... 

The properties of most common commercial proppants measured according to standardized tests are summarized in Table 10.26. 

In deep formations with high closure pressure, proppant may create a more conductive fracture than can be retained after closure of an add-etched fracture. This is also true in shallow, soft carbonates. A propped fracturing treatment may create a longer effective fracture length because fluid properties, especially leak-off, are not compromised by reactivity. 

In naturally fractured carbonates, propped fracturing may not be appropriate because of the difficulty in placing necessary amounts of proppant. The tortuous paths often present and complex stress properties can result in fracture geometry that is convoluted that it becomes impossible to maintain proppant injection. 

---