A common issue encountered by drilling engineers during drilling operation in oil and gas industries is that simple waterbased muds are not suitable for deeper depth and certain clay-swelling formations. Another option as to increasing the density of the drilling mud which brings about an increase in filtration loss, additives may be added to improve the fluid properties. This paper aims on determining the effectiveness of common salts, sodium chloride (NaCl) and potassium chloride (KCl), and haematite on the rheological properties of optimized carboxymethyl cellulose (CMC)-bentonite and partially hydrolyzed polyacrylamide (PHPA)-bentonite muds. Both CMC and PHPA polymer act as fluid loss-reducing agents and viscosifiers for normal bentonite water-based mud. The mud is further enhanced to counter certain swelling formations such as shale through the addition of NaCl and KCl. These salts inhibit the shale formation from swelling through its ions by entering the lattice of the drilling mud or formation instead of the water ions. Haematite, on the other hand, basically functions to increase mud density and acts as a substitute for barite. The effect of haematite on drilling fluid was studied because it gives higher degree of rheological parameters and increases density as compared to barite. So, an optimized concentration of additives was determined for both CMC-bentonite and PHPA-bentonite mud systems, respectively. Three grams of KCl and 3 g haematite were used for CMC-bentonite mud, while 3 g KCl and 1 g haematite were added into PHPA-bentonite mud. Both these muds have shown swelling reduction as compared to those without the use of additives. Moreover, they exhibited Herschel-Bulkley fluid behaviour according to the power law model where their 'n' value was less than 1, while their yield points were more than zero. Since shale sloughing is a major problem faced during drilling operation, it leads to major complications in drilling. So, finally, both the formulated drilling fluids are tested to analyse their effect in shale formations by static immersion test. The shale rock was collected from Champhai District of Mizoram. Both the formulated muds exhibited great results as swelling in shale rock was reduced for both muds and optimum rheological values were maintained.

The drilling of the wells from surface to target location with conventional drilling fluids may impair production and ultimate recovery by failing to adequately connect the reservoir with the wellbore by damaging the producing interval. One of the most common ways of damaging a formation is the filtration loss. Non Damaging Drilling Fluid (NDDF) is a clay and barite free environmental friendly polymer mud system mostly used in pay zone sections of development wells and specifically in horizontal drilling to avoid formation damage. Starches [(C6H10O5) n] are an environment-friendly drilling mud additive for water-base drilling fluids used to control the filtration loss. This paper reports the effect and optimum composition of Pre-Gelatinized Starch (PGS) as a filtration control component in the NDDF. PGS is a high-quality nonionic polysaccharide having the Chemical Formula: C27H48O20 and Molecular Weight: 692.658020 [g/mol] which controls the filtration loss by sealing the walls of the borehole due to its long chains of monosaccharide. Some clay specifically the montmorillonite a member of the smectite group that generally also found in the payzones of Geleki Oilfield of Upper Assam Basin absorb hydrogen ions into their structure when comes in contact with fresh water and causing swelling of the clay resulting in a reduction of the pore volume and possibly plug in the pore throats. Therefore the filtration loss should be as low as possible by forming high quality low permeable mud cake of as thin as possible. In this work, an attempt has been made to study the effect of varying composition of PGS on the different mud properties of laboratory formulated NDDF and to choose its optimum composition based on the required mud parameters of the study area.Int J Appl Sci Biotechnol, Vol 3(2): 291-300 DOI: http://dx.doi.org/10.3126/ijasbt.v3i2.12552

Crude oil needs to be transported from oil wells to refinery and storage facilities in one form or another to ultimately become end use products. After the successful extraction of oil from the ground it is mostly transported through pipelines where the crude oil experiences various changes in its physical and chemical properties. These rheological changes may cause numerous flow assurance problems such as wax and paraffin deposition which ultimately restricts the flow of oil. Chemical additives such as Pour Point depressants (PPDs) are used in this case for the efficient transportation of crude oil by lowering the Wax Deposition Temperature (WAT). Hence, in order to enhance the knowledge about PPDs, the mechanism of various types of Pour Point Depressant for aiding the flow of crude oil while transportation were discussed in this paper.

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