Performance of Fracturing Fluid Loss Agents Under Dynamic Conditions

Abstract

Fluid loss agents for crude oil and for water have been studied in dynamic tests. A treatment using a spearhead with a fluid loss agent followed by plain fluid appears feasible in crude oil, but not in water. An equation for spearhead depletion shows that spurt loss relative to fracture width must be low, if the portion of spearhead fluid in the treatment is to be small.The presence of colloidal matter in crude oils aids the fluid loss agent. Unlike in kerosene, where flow limited the agent deposition, in crude oils the filter cake continually formed and leak-off declined. The volume-time relation varied somewhat for different crudes, but was best described by a square root of time function. Spurt loss was inversely proportional to agent concentration. After the fluid loss agent initiated the filter cake, the crude oil colloids built on it effectively. A 2-minute or a 5-minute spearhead with double the normal agent concentration gave the same fluid loss curve as the same concentration did for a 30-minute test.The agents tested in water gave fluid loss plots on which, for the first few minutes, volume was proportional to the square root of time, but later became proportional to time. For fracture area calculation the customary square root of time function is a satisfactory approximation. Leak-off rates and spurt losses were higher in water systems than in oils. The spurt loss tended to be inversely proportional to concentration. In spearhead tests, the filter cakes were not eroded by water flow. However, the rather high spurt loss values make spearhead treatments impractical for water-based fluids.

Layered Modulus Effects on Fracture Propagation, Proppant Placement, and Fracture Modeling

“…Again, this variable has been exhaustively discussed in the literature including wall building characteristics of specific fluid systems, effects of natural fractures, behavior of fluid loss additives, etc. [7][8][9][10][11][12][13][14][15][16] • Tip Effects. This controls the net pressure required, at the fracture perimeter or fracture tip, to propagate the fracture.…”

Overview of Current Hydraulic Fracturing Design and Treatment Technology-Part 2

“…API has established sand-~uality specifications for use in fracturing treatments. 8 These basically cover size distribution, sphericity and roundness, solubility in acid, silt and clay content, and crush resistance. The size designations for fracturing sands are given in Table 3.…”

“…Some desirable features of a fluid for most fracturing treatments include: (1) low fluid loss to obtain the desired penetration with minimum fluid volumes; (2) sufficient effective viscosity to create the necessary fracture width, and to transport and distribute the proppant in the fracture as required; (3) no excessive friction in the fracture; (4) good temperature stability for the particular formation being treated; (5) good shear stability; (6) minimal damaging effects on formation permeability; (7) minimal plugging effects on fracture conductivity; (8) lowfriction-loss behavior in the pipe; (9) good posttreatment breaking characteristics; (10) good posttreatment cleanup andflowback behavior; and (11) low cost. Comprehensive details on all the fluids and their design information are outside the scope of this paper.…”

Simulation of Hydraulic Fracturing in Low-Permeability Reservoirs

“…W o =1.9121, ...... (11). EH f where J1 app is the apparent viscosity, Q the full well rate (two wings assumed) and H f is the fracture height.…”