Well stimulation candidates

Not all wells are good stimulation candidates. Reservoirs that have depleted pressures or low hydrocarbon volumes should be considered as too high a risk to get a return on investment for a stimulation treatment. 

Sandstone acidizing can be a very successful well stimulation method. However, the risk of failure is moderate to high. Fortunately, there are a limited number of reasons why acid treatments fail in sandstones. Success begins with the selection of a viable acidizing candidate well. Many poorly producing wells are not viable acidizing candidates. Conversely, many relatively prolific producers are the very best acidizing candidates. Once a viable candidate is selected, a systematic approach to the selection of fluids, additives, and acid placement technique must be taken. On-site quality control and posttreatment evaluation help to ensure successful results and improved future treatments. 

Another reason for failure that is part of the risk with stimulation, including acidizing, is the possibility that the treated well is a poor stimulation candidate. This is usually because the information needed to fully evaluate the well... 

Fortunately, there are many good wells and good acid stimulation candidates— far more than is generally realized. Most potential causes of add treatment failure can be addressed through a systematic approach to candidate selection and treatment design. 

This process begins with investigation and assessment of the stimulation candidate well to ascertain whether sufficient productivity improvement is, in fact, possible. Then, it is necessary to evaluate the damage present, as well as the reservoir quality and mineralogy, to determine the appropriate fluids needed. These considerations include acids, acid types, concentrations, and volumes. The proper additive program must then be determined, avoiding excessive or unnecessary additives. 

It is the aim of sandstone acidizing treatments to reduce that portion of the total skin s) that is due to damage s). Skin damage must be present, but it must be acid removable, as manifested in the wellbore, in the perforations, and/or within the formation. In evaluating a well producing from a sandstone reservoir as a stimulation candidate, skin must be measured—or at the least, assessed as best as possible— to select the proper course of treatment (or nontreatment). 

In any discussion about acidizing, organic deposits and their removal must be discussed. The deposition of organic material is a common damage mechanism, and its possible presence in an oil well that is a potential stimulation candidate must always be explored. This chapter briefly addresses organic deposition problems and solutions. 

The Advanced Purchase Commitments approach proposed by Kremer and Glennerster (2004) and the Center for Global Development (2005) has attracted considerable public attention as well as seed funding from the Gates Foundation in recent years. Advanced purchase commitments could be useful for certain types of pharmaceutical products, principally vaccines, to stimulate research by promising a subsidy of a fixed value per unit for a given number of units. The most attractive candidate product for such a commitment is a malaria vaccine, since the health (and economic) benefits from an effective malaria vaccine could be very large. 

Whereas several peptides besides AVP are known to act synergistically with CRH, the only peptide candidate in humans that inhibits the HPA system at all regulatory levels of the system seems to be atrial natriuretic peptide (ANP). ANP has been shown to inhibit the stimulated release of CRH and ACTH in vitro and in vivo. This could be observed in humans as well, where ANP inhibits the CRH-induced ACTH (Keller et al. 1992), prolactin (Wiedemann et al. 1995), and cortisol secretion (StrOhle et al. 1998). ANP is not only synthesized by atrial myocytes (deBold et al. 1985) and released into the circulation, but is also found in neurons of different brain regions (Tanala et al. 1984) where specific receptors have been found. ANP receptors and immunoreactivity have been found in periventricular and paraventricular hypothalamic nuclei, the LC, and the central nucleus of the amygdala. 

The pylorus-ligated rat has been proven to be a valuable method to evaluate the secretory (versus basal secretion) as well as the antisecretory potential (versus stimulation with histamine, gastrin, or carbachol) of a candidate compound with various secretory or antisecretory mechanisms of action. 

In addition to the serine-threonine phosphorylation sites modulated by PKC and PKA, a basal state of tyrosine phosphorylation exists in platelet TP receptors, as in bradykinin receptors, and this phosphorylation increases on agonist stimulation (166). The tyrosine kinase responsible for this pho horylation, as well as that of the parallel phosphorylation of phosphatidylinositol 34dnase (PIj4dnase), that occurs on agonist stimulation, is unknown, but p27 known to be activated by TP receptor agonists (167), is a candidate (166). It is also possible that PI, kinase itself might phosphorylate TP receptors. The functional role of tyrosine kinase-mediated phosphorylation of TP receptors is unknown. 

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