The Effect of Wormholing on the Fluid Loss Coefficient in Acid Fracturing

1995 ◽  
Vol 10 (04) ◽  
pp. 257-264 ◽  
Author(s):  
A.D. Hill ◽  
Ding Zhu ◽  
Y. Wang
Keyword(s):  
Loss Coefficient ◽  
Fluid Loss ◽  
Acid Fracturing

Acid Filtration in Dynamic Conditions to Mimic Fluid Loss in Acid Fracturing

1997 ◽  
Author(s):  
B. Bazin ◽  
C. Roque ◽  
G. Chauveteau ◽  
M. Bouteca
Keyword(s):  
Fluid Loss ◽  
Dynamic Conditions ◽  
Acid Fracturing

Characteristics of Acid Reaction in Limestone Formations

1971 ◽  
Vol 11 (04) ◽  
pp. 406-418 ◽  
Author(s):  
D.E. Nierode ◽  
B.B. Williams
Keyword(s):  
Transfer Rate ◽  
Reaction Rate ◽  
Mass Transfer Rate ◽  
Field Conditions ◽  
Rock Surface ◽  
Fluid Loss ◽  
Matrix Acidizing ◽  
Acid Fracturing ◽  
Acid Reaction ◽  
Flow Through

Abstract A kinetic model for the reaction of Hydrochloric acid with limestone bas been determined. Reaction order and rate constant for this model were calculated from experiments where acid reacted with a single calcium carbonate plate. Experiments were performed so that acid flow past the plate and mass transfer rate to the rock surface could be calculated theoretically. The resulting model, therefore, accurately represents the acid reaction process at the rock surface and is independent of mass transfer rate. Combination of this model with existing theory allows prediction of acid reaction during acid fracturing operations. A model for acid reaction in wormholes created during matrix acidization treatments is presented along with data for reaction of hydrochloric, formic and acetic acids in a wormhole. Factors limiting stimulation in acid fracturing or matrix acidizing treatments are then discussed. Introduction To predict the stimulation ratio resulting from acid fracturing or matrix acidizing treatments it is necessary to know the rate of acid reaction under field conditions. In acid fracturing treatments, for example, reaction occurs as acid flows through a narrow fracture. Reaction in a matrix treatment occurs during flow through wormholes (channels of roughly circular cross-section) created by acid reaction. In both treatments, a large amount of mixing occurs during flow through the fracture or channel as a result of tortuosity and wall roughness. Reaction rate can be obtained from experiments, or predicted by theoretical calculations that accurately model field conditions. In general a theoretical procedure is preferred since it can be used without recourse to laboratory testing. Acid-reaction-rate data have been reported from a number of experiments intended to simulate acid reaction in field treatments. Tests most often used are:the static reaction rate test, in which a cube of limestone is contacted with unstirred acid at a known ratio of rock surface area to acid volume;flow experiments, where acid is forced to flow between parallel plates of limestone; anddynamic tests, whine limestone specimens are rotated through an agitated acid solution. In general, these tests model some aspects of the reaction process, such as area to volume ratio, or acid flow velocity, but do not accurately model all field conditions. To obtain an accurate mathematical model for field treatments, assuming fracture or wormhole geometry is known, it is necessary to characterize acid reaction kinetics at the limestone surface, rate of acid transfer to the surface, and rate of fluid loss from the fracture or wormhole. (Each of these processes is shown schematically in Fig. 1.) processes is shown schematically in Fig. 1.) Reaction kinetics are independent of the geometry in which reaction occurs; therefore, once kinetics have been determined for a given acid-rock system field treatments can be simulated by prediction of the rate of acid transfer to the surface and fluid loss to the formation. Unfortunately, experiments reported to dare do not allow determination of a kinetic model. SPEJ P. 406

An Analysis of the Acidizing Process in Acid Fracturing

1973 ◽  
Vol 13 (04) ◽  
pp. 239-250 ◽  
Author(s):  
H.R. van Domselaar ◽  
R.S. Schols ◽  
W. Visser
Keyword(s):  
Hydrochloric Acid ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Acid Concentration ◽  
Fluid Loss ◽  
Flow Conditions ◽  
Fracture Width ◽  
Acid Fracturing ◽  
Fracturing Process ◽  
Turbulent Flow Conditions

Abstract The theoretical analysis of the acid-fracturing process for turbulent-flow conditions has been process for turbulent-flow conditions has been reconsidered taking fluid losses into account. For a simple fracture model and an idealized acidizing process, the acid concentration in the fracture process, the acid concentration in the fracture during acid injection and the fracture width have been determined as functions of time and place for three loss conditions:no fluid loss,fluid loss proportional to time, andfluid loss proportional to the square root of time. proportional to the square root of time. From the results of the analysis, it is concluded that even under the unfavorable conditions of turbulent flow in the fracture and fluid loss, acid penetration is, in general, not a limiting factor in penetration is, in general, not a limiting factor in the application of the acid-fracturing process. However, it will not be possible to predict the productivity increase resulting from a given productivity increase resulting from a given treatment until more experimental data on the conductivity of etched fractures and on certain aspects of the reaction kinetics have been gathered. Introduction Acid-fracturing treatments are frequently applied to improve well productivity in limestone formations. In this process, hydrochloric acid is injected into a hydraulically induced fracture, which extends diametrically from the wellbore into the formation. During injection, the limestone faces of the fracture are dissolved. As a result, acid is consumed and its concentration decreases in the direction of flow. The width of the fracture increases, and the fracture faces may become irregularly etched as a result of the natural anisotropies of the formation. The etching pattern produced may contribute to an improvement in fracture conductivity after the fracture is allowed to close. The extent of this etching into the fracture and its final fluid conductivity determine the increase in productivity. Barron et al. have presented an empirical formulation of the acid-fracturing process for laminar flow conditions without fluid loss. When a theoretical description given by Prins et al. concerning the heat-transfer in laminar flow between parallel plates, is applied to the acid-fracturing parallel plates, is applied to the acid-fracturing process, the acid concentration in a fracture for process, the acid concentration in a fracture for steady-state laminar flow can be exactly described, provided that the fracture width is constant and no provided that the fracture width is constant and no fluid loss occurs. A comparison of the acid concentrations calculated from the empirical reaction-rate data of Barron with those theoretically derived according to Prins shows that these values are of the same order of magnitude and can be made equal for acceptable values of the diffusion rate only in the range of low velocities. Judging from the experimental set-up of Barron, we believe that for higher velocities the entrance transition length for fully developed laminar flow should be longer. For this reason, no agreement in the higher velocity ranges can be expected. This view is supported by Williams et al., who compared theoretically derived reaction rates in the heterogeneous calcium-carbonate /hydrochloric-acid system with those of Barron et al., who also conclude that entry effects may be responsible for the discrepancies in the higher velocity range. Nierode and Williams determined a kinetic model for the heterogeneous reaction of hydrochloric acid with limestone. The reaction order and rate constant used in their model were obtained from experiments. On the basis of this model, they derived an acid-fracturing design for laminar flow conditions including fluid loss. In the study described below, the acid-fracturing process has been reconsidered for turbulent-flow process has been reconsidered for turbulent-flow conditions in which both fluid loss and change in fracture width have been taken into account. We feel that the study provides a more realistic description of the process for both a vertical and horizontal fracture and that it may be used as a bask for designing acid-fracturing treatments. MATHEMATICAL DESCRIPTION OF THE ACIDIZING PROCESS FOR A RECTILINEAR FRACTURE A vertical rectangular fracture (rectilinear) with initially plan-parallel and flat fracture faces was adopted as a fracture model. SPEJ P. 239

A Model of the Fractal Fluid Loss Coefficient and its Effect on Fracture Length and Well Productivity

2015 ◽  
Vol 51 (2) ◽  
pp. 168-180
Author(s):  
Guofa Ji ◽  
Zhaozhong Yang ◽  
Xiaogang Li ◽  
Yanjun Lu ◽  
Dan Luo
Keyword(s):  
Loss Coefficient ◽  
Fluid Loss ◽  
Well Productivity ◽  
Fracture Length

scholarly journals Erratum to: A Model of the Fractal Fluid Loss Coefficient and its Effect on Fracture Length and Well Productivity

2015 ◽  
Vol 51 (3) ◽  
pp. 330-330
Author(s):  
Goufa Ji ◽  
Zhaozhong Yang ◽  
Xiaogang Li ◽  
Yanjun Lu ◽  
Dan Luo
Keyword(s):  
Loss Coefficient ◽  
Fluid Loss ◽  
Well Productivity ◽  
Fracture Length

Fluid-Loss Control: The Key to Successful Acid Fracturing

1989 ◽  
Vol 4 (02) ◽  
pp. 215-220 ◽  
Author(s):  
C.W. Crowe ◽  
B.H. Hutchinson ◽  
B.L. Trittipo
Keyword(s):  
Fluid Loss ◽  
Acid Fracturing ◽  
Loss Control

scholarly journals Analysis of the Colebrook-White Equation and further approaches to solve Fluid Loss Coefficient Definition Problems

2020 ◽  
pp. 97-115
Author(s):  
Yan Oliveira Vasconcellos ◽  
Francisco Jarmeson Silva Bandeira ◽  
Leonardo Dias Pereira ◽  
Flavio Maldonado Bentes ◽  
Marcelo de Jesus Rodrigues da Nóbrega ◽  
...  
Keyword(s):  
Loss Coefficient ◽  
Fluid Loss
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