A preliminary screening and characterization of suitable acids for sandstone matrix acidizing technique: a comprehensive review

Matrix acidizing is a broadly developed technique in sandstone stimulation to improve the permeability and porosity of a bottom-hole well. The most popular acid used is mud acid (HF–HCl). It is a mixture of hydrofluoric acid and hydrochloric acid. However, one of the conventional problems in sandstone acidizing is that mud acid faces significant issues at high temperature such as rapid rate of reaction, resulting in early acid consumption. This downside has given a negative impact to sandstone acidizing as it will result in not only permeability reduction, but can even extend to acid treatment failure. So, the aim of this study is to provide a preliminary screening and comparison of different acids based on the literature to optimize the acid selection, and targeting various temperatures of sandstone environment. This paper has comprehensively reviewed the experimental works using different acids to understand the chemical reactions and transport properties of acid in sandstone environment. The results obtained indicated that fluoroboric acid (HBF4) could be useful in enhancing the sandstone acidizing process, although more studies are still required to consolidate this conclusion. HBF4 is well known as a low damaging acid for sandstone acidizing due to its slow hydrolytic reaction to produce HF. This would allow deeper penetration of the acid into the sandstone formation at a slower rate, resulting in higher porosity and permeability enhancement. Nevertheless, little is known about the effective temperature working range for a successful treatment. Considering the pros and cons of different acids, particularly those which are associated with HF and HBF4, it is recommended to perform a comprehensive analysis to determine the optimum temperature range and effective working window for sandstone acidizing before treatment operation. Prior to sandstone acid stimulation, it is essential to predict the feasibility of acid selected by integrating the effects of temperature, acid concentration and injection rate. Therefore, this manuscript has thrown light into the research significance of further studies

Seeking Coherence in Doctrines of Party Election Expenditures

Federal Election Commission v. Colorado Republican Federal Campaign Committee, 213 F.3d 1221 (10th Cir. 2000), cert. granted, 121 S. Ct. 296 (2000) (00-191). The 2000 election marked a decisive step in the rebirth of political parties as the dominant force in American elections, thanks in no small part to increased rights won in the courts at the expense of federal election law. The only major election law still constraining party expenditures on races for Congress and the Senate was, midway through the campaign, struck down in the 10th Circuit; if, on its current appeal, the Supreme Court decides against the Federal Election Commission (FEC), parties will be free make unlimited expenditures on behalf of their candidates

Securities Regulation

This Article surveys significant cases decided by the Eleventh Circuit Court of Appeals during 1991 and 1992 in the field of securities regulation. This Article also examines selected Supreme Court decisions during this survey period that affect Eleventh Circuit precedent