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Drilling into the permeable reservoir experiences the migration of drilling mud filtrate into the reservoir formation, which eventually results in the formation of flushed and transition zones within the reservoir. This interaction of drilling mud and the formation fluid in these zones usually has some profound effect on the cold flow and reservoir fluid properties when flowed to surface. An experimental work was conducted to evaluate the effect of drilling mud additive interaction with the reservoir fluid at surface conditions to find out any flow assurance-related concern during the flow back and or well commissioning. The project was started by obtaining the sample from an oil and gas field located in the Northern area of Pakistan. Initially the crude oil was classified as a lighter product with API° gravity of 49.52° and density of 782 kg/m3. The cold flow properties that include cloud point and pour point were 6 °C and – 1 °C, respectively, for the studied crude oil. During this study, the crude oil was physically interacted with four different polymeric water-based drilling mud, which belongs to three different classifications of polymers; biopolymers, synthetic, and modified polymers. Upon the interaction with different polymeric mud systems, the API° gravity changes and the maximum API° gravity obtained was 55.18° in sodium alginate system, while minimum of 45.74° was attained in PAC-L system. Moreover, similar variations were also observed in the crude oil density. The initial crude density of 782 kg/m3 increased to 798 kg/m3 in PAC-L, while substantially dropped to 758 kg/m3 in sodium alginate. In addition, the variations in the cold flow properties that include pour point and cloud point were observed after interaction between crude oil and the mud samples. No considerable change was witnessed in cloud point in any of the samples. A maximum change of 0.3 °C was perceived in cloud point after day 1 in sample contaminated with PAC-L. On the other hand, this change increased to 0.5 °C on day 10 in PAC-L and PHPA samples. All the remaining samples demonstrated cloud points closer to 6 °C, which was similar to the uncontaminated crude oil sample. Conversely, significant variation was noticed in the pour point of all the samples. Sodium alginate and pure-bore contaminated samples showed a decrease in pour point by – 5 °C and − 4.5 °C, respectively. Modified and synthetic polymeric contaminated samples show pour points closer to the initial uncontaminated crude oil sample. All these results give a conclusion that biopolymers can be used in drilling mud and it does not have any significant change on the cold flow and reservoir fluid properties which is of paramount importance while flowing back the well to commission it during the winter season when the ambient temperature drops below 0 °C. [ABSTRACT FROM AUTHOR]

This study evaluated and interpreted complex data sets of water samples collected from different sampling origins of ground water (hand pump and tube well) and surface water (municipal, river and canal). The aim was to provide information concerning the apportionment of pollution sources to obtain better information about water quality and possible distribution of As with respect to its speciation. The As (III) formed complex with ammonium pyrrolidinedithiocarbamate (APDC) and extracted by surfactant-rich phases in the non-ionic surfactant Triton X-114, while total iAs in water samples was adsorbed on titanium dioxide (TiO2) and determined by electrothermal atomic absorption spectrometry. The accuracy of the proposed methodologies was confirmed by standard addition method. The recoveries of As (III) and total inorganic arsenic (iAs) were found to be >98%. The results revealed that the ground water of the area under study was more contaminated as compared to surface water samples. The mean concentration of As (III) and As (V) in the surface water samples was found to be 15.8 and 6.00 µg L−1, respectively, whereas, in the case of ground water samples, the contents of As (III) and As (V) ranged from 6.20 to 51.0 and 6.40 to 53.0 µg L−1, respectively. Principal component analysis performed on a combined (tube well and hand pump) samples data set extracted two significant factors explaining more than 60% of total variance, which suggested that the contamination sources might be natural or anthropogenic. [ABSTRACT FROM PUBLISHER]