Techniques for evaluating and improving the performance of the iron oxides used as barite substitutes in oil well drilling fluids.

Barite is the main weighting agent for drilling fluids because it has the required advantage of high specific gravity together with chemical inertness, and it is non-abrasive. Barite is frequently contaminated with alkaline soluble carbonate and sulfide minerals that are causing serious problems during drilling operations. Another problem is world reserves are estimated at about 200 million tons that will last only about twenty years.The evaluation of the various drilling mud types revealed advantages of iron oxide weighted drilling fluids over barite weighted systems. Non-dispersed iron oxide drilling fluids exhibited better rheological performance and higher stabilization characteristics at ambient and high temperature. Iron oxide weighted mud systems showed superior rheological and gel strength characteristics at high temperature. Higher penetration rates were estimated for iron oxide weighted mud types based on drilling fluids properties alone. Iron oxide muds were less reactive with shale cuttings than barite mud and therefore less liable to cause borehold problems.In searching for a substitute for barite, this work was designed to evaluate and improve the performance of a selected group of iron oxides in drilling fluids. Iron minerals evaluated in this study were: Ilmenite, under the commercial name of "Bargain"; Itibirite, composed of natural hematite ore, with small amounts of quartz under the commercial name of "Densimix"; and Synthetic Hematite, a biproduct resulting from the processing of various iron oxides and sulphides produced by Kerr-McGee Chemical Corporation.This study shows evidence that there are prospects for salvage of the iron minerals from the drilling fluids after the well completion which will make the utilization of iron minerals more economical than barite.The mineral grain attrition of the iron oxides is slower and less destructive to mud properties. Special mud formulation incorporating polymer additives can be utilized to either eliminate or reduce the mud wear effect and grain attrition of solids. The polymer additives act as coating agents to the abrasive weighting material and encapsulates the shale cuttings to prevent or minimize hydration effects

Isolation of human genomic DNA for genetic analysis from premature neonates: A comparison between newborn dried blood spots, whole blood and umbilical cord tissue

Background: Genotyping requires biological sample collection that must be reliable, convenient and acceptable for patients and clinicians. Finding the most optimal procedure of sample collection for premature neonates who have a very limited blood volume is a particular challenge. The aim of the current study was to evaluate the use of umbilical cord (UC) tissue and newborn dried blood spot (DBS)-extracted genomic DNA (gDNA) as an alternative to venous blood-derived gDNA from premature neonates for molecular genetic analysis. All samples were obtained from premature newborn infants between 24-32weeks of gestation. Paired blood and UC samples were collected from 31 study participants. gDNA was extracted from ethylenediaminetetraacetic acid (EDTA) anticoagulant-treated blood samples (~500μl) and newborn DBSs (n = 723) using QIAamp DNA Micro kit (Qiagen Ltd., Crawley, UK); and from UC using Qiagen DNAeasy Blood and Tissue kit (Qiagen Ltd., Crawley, UK). gDNA was quantified and purity confirmed by measuring the A260:A280 ratio. PCR amplification and pyrosequencing was carried out to determine suitability of the gDNA for molecular genetic analysis. Minor allele frequency of two unrelated single nucleotide polymorphisms (SNPs) was calculated using the entire cohort.Results: Both whole blood samples and UC tissue provided good quality and yield of gDNA, which was considerably less from newborn DBS. The gDNA purity was also reduced after 3years of storage of the newborn DBS. PCR amplification of three unrelated genes resulted in clear products in all whole blood and UC samples and 86%-100% of newborn DBS. Genotyping using pyrosequencing showed 100% concordance in the paired UC and whole blood samples. Minor allele frequencies of the two SNPs indicated that no maternal gDNA contamination occurred in the genotyping of the UC samples.Conclusions: gDNAs from all three sources are suitable for standard PCR and pyrosequencing assays. Given that UC provide good quality and quantity gDNA with 100% concordance in the genetic analysis with whole blood, it can replace blood sampling from premature infants. This is likely to reduce the stress and potential side effects associated with invasive sample collection and thus, greatly facilitate participant recruitment for genetic studies. © 2013 Rajatileka et al.; licensee BioMed Central Ltd