Produced Water Geochemistry from an Upstream Oil Operation

Oil and gas industries generate a significant amount of water during the production. The composition of this water varies with the geologic age, depth, and geochemistry of the region along with the chemicals added during the process. Geochemistry of formation water is used for aquifer identification, pollution problems, water compatibility studies, corrosion monitoring, water-quality control, water flooding, exploration, and to diagnose wellbore integrity issues. The current study investigates the spatial and temporal variation of produced water geochemistry from one of the largest conventional oil field, Ghawar field, Saudi Arabia. Produced water from different wellheads were collected and analyzed for different geochemical characteristics. Sixteen wells from ABQQ, nineteen wells from ANDR and twenty wells from SDGM area were selected for the current study. Sampling and analysis were performed as per the standard procedures. Results indicated that the pH of the sample varied from 6.0 to 7.4, and Electrical conductivity from 94200 to 102690 μS/cm. The spatial variation of major cations and anions were also recorded and represented by graphical plots. Metal analysis indicated the highest concentration for boron, which is 20.5 mg/L at ABQQ area, whereas all other metals are very low in concentration. Temporal variation of a single well at SDGM area indicated drastic change in the ionic concentration, whereas the geochemistry remains same as indicated by Tickler plot. The water type of the respective area was studied by tickler plots, which indicated same source of formation water in different wells at ABQQ, ANDR and SDGM areas. The ionic concentration is also used to predict corrosion and scaling issues. By Langelier Saturation Index (LSI) and Ryznar Stability Index (RSI), the sample from all the wells showed higher scaling potential. The study concludes that the water type in different areas under Ghawar field remains same regardless of drastic changes in the ionic concentration, which can be used to diagnose wellbore integrity issues.

Using tickler chains to promote more environmentally benign trawls in an Australian penaeid fishery

There has been an increasing emphasis on reducing the environmental impacts of penaeid trawls by modifying their anterior sections.In one Australian estuary,this approach has culminated in a new generic trawl comprising a slightly smaller mesh size,and steeper and shorter side panels than traditional trawls,combined with a top panel extending forwards of the bottom panel(termed‘lead-ahead’)and no headline floats.This study sought to investigate if an additional simple,cumulative modification(tickler chain)might help promote adoption of the new trawl,via improved penaeid catches.Six volunteer fishers towing pairs of either the traditional or new trawls in double rigs were asked if an observer could accompany fishing trips,and alternately attach a light tickler chain(~3 kg)anterior to the ground gear of one trawl.Regardless of the trawl design,the tickler chains significantly increased the catch weights of penaeids,but relatively more so in the new trawls(by 1.11×vs 1.08×).The tickler chains also significantly increased the number and weight of total bycatch in the traditional trawls(by up to 1.22×),but not in the new trawls-although there were variable species-specific effects.In terms of total effects,the data support using tickler chains to increase the efficiency of the new trawls and their cumulative benefits,and could be promoted to facilitate broader inter-and intra-fleet adoption.

Refining tickler chains for penaeid trawls

Tickler chains are simple additions to the ground gears of benthic trawls that can improve the catches of some target species,albeit with considerable variability.The purpose of this study was to decipher some of the technical variability associated with tickler chains used with generic,paired trawls targeting school prawns,Metapenaeus macleayi.In the first of two experiments,single tickler chains were either attached between the trawl otter boards or the wing ends and compared against each other and a control trawl(no tickler chain).Attaching the tickler chain to the otter boards significantly reduced wing-end spread and the trawled area without significantly affecting catches of school prawns.By comparison,attaching the tickler chain to the wing ends maintained spread and resulted in significantly more school prawns being caught(by 1.11×)than in the control trawl,and also fewer numbers of one teleost species,pink-breasted siphonfish,Siphamia roseigaster.In experiment two,a single tickler chain was compared against one with multiple chains and one with a double chain;all attached at the wing ends.Trawls with the multiple-and double-tickler chains had the same wing-end spread as those with the single tickler chain,while retaining up to 1.17×more school prawns,and for the double-chain tickler,45%fewer southern herring,Herklotsichthys castelnaui.The results are attributed to mechanical and visual stimuli affecting school prawns and some fish,respectively,and support maximising the surface area of tickler chains within the wing ends as a means for improving penaeid-trawl species selectivity without affecting swept area.

Improving penaeid-trawl efficiencies via ground gear with tickler chains

Penaeid trawls often have poor ecological efficiencies measured as unwanted bycatches(with high discard mortality)and<100%effectiveness for all penaeids interacting with the ground gear(with some escape mortality).This study investigated the utility of varying ground-chain size(8-vs 10-mm diameter(Ø)stainless-steel chain)and the present or absence of a tickler chain(4-mmØ)for improving efficiencies an Australian fishery diurnally targeting school,Metapenaeus macleayi and eastern king prawns,Penaeus plebejus.There were no treatment effects on wing-end spread and therefore areas trawled.Irrespective of the tickler chain,increasing the ground-chainØreduced catches of total penaeids(by 14%)and jellyfish,Catostylus mosaicus(by 39%)-results speculatively attributed to variation in ground contact and/or a slightly higher footrope in trawls with the 10-mmØchain.By comparison,installing the tickler chain had no effect on eastern king prawns,but increased catches of school prawns(by 1.13×)and bycatches of blue swimmer crabs,Portunus armatus(1.52×;a species with a low discard mortality)and jellyfish(1.23×),while reducing bycatches of two species with high discard mortalities:southern herring,Herklotsichthys castelnaui(by 38%)and squid,Uroteuthis sp.(37%).The results were attributed to the tickler chain producing(1)mechanical stimuli that augmented the capture of benthic-orientated school prawns(but not eastern king prawns owing to diel variations in emergence from the substrata),blue swimmer crabs and jellyfish;and(2)visual stimuli that possibly enabled some southern herring and squid to detect the trawl and escape.The data show tickler chains can improve trawl efficiency for penaeids with at least some positive effects on bycatch that should be rationalised in terms of species-specific vulnerabilities to unaccounted fishing mortality.