Stimulation treatment fracturing

The flowback of a proppant following fracture stimulation treatment is a major concern because of the damage to equipment and loss in well production. The mechanisms of flowback and the methods to control flowback have been recently discussed in the literature [ 1343]. To reduce proppant flow-back, a curable resin-coated proppant can be applied [1349]. The agent must be placed across the producing interval to prevent or reduce the proppant flowback. 

Read, D.A. and Wells, G.L. "Measurement While Fracturing for Comparing and Optimizing the Performance of Well Stimulation Treatments," 1985 Proc. Annu. Southwest Pet. Short Course, 171 176. 

The types of stimulation treatments available on the market today are almost as varied as the number of formations that produce hydrocarbons. Stimulations can be categorized into four primary types hydraulic fractur-... 

Foamed Matrix Acidizing. Matrix addizing is a stimulation treatment used to remove damage near the wellbore without deating a fracture. The process involves the injection of a reactive fluid into the porous medium at a pressure below the fracturing pressure. The fluid dissolves some of the porous medium and consequently increases its permeability. 

The use of the bottomhole treating pressures enables the fracture parameters to be calculated more accurately. As well, the continuous or dispersed phases can be altered as the treatment progresses in order to achieve maximum fracture propagation. The more accurate the prediction of the bottomhole pressures, the more reliable the data can be to create the best possible stimulation treatment. 

Unbroken gel will cause damage. Most fracturing fluids are designed to break viscosity either on their own or by inducement with specific gel breaker additives. Gel must break down in viscosity to a thin fluid that easily flows back following fracturing stimulation treatment. Gel plugging may result if an improper or inadequate breaker is used. 

In natural fractures, the ratio of surface area to acid volume is much less, and deeper treatment is possible. In fracture acidizing, the ratio of rock surface area to acid volume is even lower. Very deep stimulation in fracturing applications is therefore possible, espedally with slower-reacting, low-leak-off add systems. 

It is important to evaluate the effectiveness of every stimulation treatment. Evaluations of matrix addizing and add fracturing treatments are usually based on production increases or comparison with other wells. With matrix acidizing, comprehensive pretreatment and posttreatment well testing and interpretation are usually not economically justified. Comprehensive evaluation can be justified most of the time with acid fracturing and propped fracturing. 

Fluoride stimulates bone formation by protein kinase activation mediated effects on osteoblasts. Fluorides have been used in the treatment of osteoporosis, but their anti-fracture effect is not undisputed. 

A major regulator of bone metabolism and calcium homeostasis, parathyroid hormone (PTH) is stimulated through a decrease in plasma ionised calcium and increases plasma calcium by activating osteoclasts. PTH also increases renal tubular calcium re-absorption as well as intestinal calcium absorption. Synthetic PTH (1-34) has been successfully used for the treatment of osteoporosis, where it leads to substantial increases in bone density and a 60-70% reduction in vertebral fractures. 

The production of natural gas from coal typically requires a stimulation with hydraulic fracturing. Basic studies on the effectiveness of various treatment methods for coal-beds have been presented in the literature [398,1424]. 

Acids were an early exception to the no water rule. It was recognized that aqueous solutions of acids would inhibit swelling of clays and shales as well as dissolve any acid-soluble minerals contained in a formation. By 1933 commercial well stimulation with hydrochloric acid was of great interest. A whole separate methodology and treatment chemistry has since evolved around acidizing and fracture acidizing(54). Water emulsions, mainly emulsified acids, and gelled acids thickened with polymeric additives were applied early in the history of well treatment. 

Several articles with informative bibliographies covering formation protection additives have appeared recently(97,101,102). The exact rock formation sample in question, the ionic strength of the treatment fluid, the preventive additives that are present, the pH of the fluid, and the test procedure employed all have significant effects on the test results. However, with careful experimentation using representative materials a preventive additive package can be administered as part of a water-based fracture treatment to allow effective stimulation of most hydrocarbon reservoirs. Because of this, water-based fracturing fluids are used in approximately 90% of all fracture treatments performed today. 

Raloxifene is a SERM devoid of stimulating effects on the uterus as is known from the initial studies (Delmas et al. 1997). Eliminating one of the major concerns raised by the experience gained with tamoxifen studies, both in prevention and adjuvant treatments, puts raloxifene in a place of privilege to be a rational alternative agent. At the same time it improves bone density, prevents osteoporosis and vertebral fracture, and reduces cardiovascular events in a subset of high-risk patients (Silverman et al. 2004). The evidences on the effects of raloxifene on the uterus are explained in detail in Chap. 10 of this book. 

A conflict arises from two claims the first, that fluoride stimulates new bone growth and hence is useful therapeutically in controlling osteoporosis, and the other, that it is the cause of the increasing prevalence of hip fractures in the elderly [6]. Fluoride is currently not recommended for the treatment of osteoporosis, although slow release fluoride therapy is reportedly beneficial. The long-term benefit of the latter is unknown [7]. 

Teriparatide, the recombinant form of PTH 1-34, is approved for treatment of osteoporosis. Teriparatide is given in a dosage of 20 meg subcutaneously daily. Like fluoride, teriparatide stimulates new bone formation, but unlike fluoride, this new bone appears structurally normal and is associated with a substantial reduction in the incidence of fractures. Teriparatide is approved for use for only 2 years. Trials examining the sequential use of teriparatide followed by a bisphosphonate after 1 or 2 years are in progress and look promising. Giving teriparatide with a bisphosphonate has not shown greater efficacy than the bisphosphonate alone. 

Stimulation fluid is a treatment fluid prepared for stimulation purposes, although the term most commonly is applied to matrix stimulation fluids. Most matrix stimulation fluids are acid or solvent-based, with hydrochloric acid being the most common base due to its reaction characteristics and its relative ease of control. Matrix stimulation is a process of injecting a fluid into the formation, either an acid or solvent at pressures below the fracturing pressure, to improve the production or injection flow capacity of a well. 

Osteoporosis is of two forms- primary i.e. idiopathic and secondary. Primary osteoporosis is classified into type I and type II osteoporosis. Type I is referred to post menopausal osteoporosis which is the main type affecting women, characterized by rapid bone loss and affects women after the menopause, mainly in trabecular bone and is associated with vertebrae and distal radio fractures whereas type II also termed as senile osteoporosis occurs due to chronic deficiency of calcium, increase in parathormone activity and decrease in bone formation and is associated with aging. On the other hand secondary type results from inflammatory processes, endocrine changes, multiple myeloma, sedentariness and the use of drugs such as heparin, corticoid and alcohol [3]. Prevention is the main treatment of osteoporosis, for which bone mass peak and the prevention of postmenopausal reabsorption are critical elements. The common treatment of osteoporosis includes calcium consumption as calcium salts, vitamin D supplements, and hormone reposition [4], the use of calcitonin to modulate serum levels of calcium and phosphorous [5], the use of bisphosphonate, mainly alendronates [6], use of ipriflavone and sodium fluoride [7], besides physical activity to strengthen muscles, stimulate osteoblasts formation and prevent reabsorption. 

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