Unlocking Surface Constraints for High Temperature Gas Field: Production Network Compositional Variation Analysis for Wet Gas Meter PVT Calibration Approach

Installation of Wet Gas Metering System (WGMS) on a platform for the purposes of real-time measurement of liquid and gas production rates as well as performance monitoring as part of reservoir and production optimization management are quite common nowadays in Malaysia. Nonetheless, understanding of wells production deliverability invariably measured using these Wet Gas Meter (WGM) which provides the notion of production rates contributed by the wells are paramount important, eventually the produced fluids will be processed by various surface equipment at the central processing platform before being transport to onshore facilities. However, the traditional WGM are known to operate within ±10% accuracy, whereby the confidence level on measurement of the produced fluids can be improved either by updating with accurate PVT flash table or combination of results from performing tracer dilution technique for data verification. Sarawak Gas Field contains a number of gas fields offshore East Malaysia, predominantly are carbonate type formation, where one (1) of the field operated by PETRONAS Carigali Sdn.Bhd.(PCSB) is a high temperature accumulation at which temperature at the Gas Water Contact (GWC) approximately 185°C and full wellstream Flowing Tubing Head Temperature (FTHT) records at 157°C. Cumulative field production of five (5) wells readings from WGM had shown 9.1% differences as compared to the export meter gas readings. As part of a strategy to provide maximum operational flexibility, improvement on accuracy of the WGM is required given that the wells have higher Technical Potential (TP) but are limited by threshold of the multi-stage surface processing capacity. This also impacts commerciality of the field to regaining the cost of capital investment and generate additional revenue especially when there is a surge in network gas demand, as the field unable to swiftly ramp-up its production to fulfill higher gas demand considering the reported production figures from cumulative WGM surpassing the surface equipment Safe Operating Envelope (SOE). Our approach begins with mass balance check at the WGMS and export meter including the fuel, flare and Produced Water Discharge (PWD) to check mass conservation by phases because regardless different type of phases change occurs at topside the total mass should be conserved (i.e. for total phases of gas, condensate and water) provided that precise measurement by the metering equipment. Tracer dilution measurement of gas, condensate and water flowrates were used to verify the latest calibrated Water Gas Ratio (WGR) and Condensate Gas Ratio (CGR) readings input into the WGM. Consequently, PVT separator samples were also taken via mini-separator for compositional analysis (both gas and condensate) and for mathematical recombination at the multi-rates CGR readings to generate a representative PVT compositional table. Simultaneously, process model simulation run was conducted using full wellstream PVT input to validate total field production at the export point. This paper presents practical approach to balance the account, to ensure the SOE at topside as well as to improve the PVT composition at the WGM for high temperature field that emphasizes on understanding of compositional variations across production network causing significant differences in total field production between WGM and the allocation meter.

Tracing Heavy Metals at Nantymwyn, Wales

<p>Wales has a long history of coal and metal mining, with over 1,300 abandoned metal mines across the country. These mines pollute a number of rivers and lead to the failure of Water Framework Directive (WFD) standards for heavy metals. This includes Nantymwyn, an abandoned lead mine, which has two streams that flow into the River Tywi, and metal loads can be traced downstream for 65km. Nantymwyn, in common with many of Wales’ lead mines, has complex and poorly understood underground workings, which have degraded in the 90 years since closure. The mine is believed to have been worked during pre-Roman times and, is noted historically from AD 1530. The Nant y Bai stream flows through extensive spoil heaps, as well as over old workings, and has inflows from adits, over ground and subterranean inputs. Consequentially, conventional spot sampling of the metal concentrations as has been historically carried out by government agencies does not accurately convey the problems caused by the mine.</p><p>Tracer dilution and synoptic sampling was determined at Nantymwyn in July 2019 to calculate stream flow and heavy metal loadings and their variation downstream. Sodium bromide was injected upstream of the mine site, and once it reached a ‘plateau state’ in the stream it was sampled at 34 points over the 2km of stream. These samples were analysed for metal and bromide concentrations using Inductively coupled plasma mass spectrometry (ICP-MS), which allowed One-Dimensional Transport with Inflow and Storage (OTIS) modelling to predict pollutant flows. Additionally, monthly sampling and salt dilution flow gauging at 12 sites along the stream has been conducted since February 2019. The second, smaller stream at Nantymwyn is monitored monthly at six points.</p><p>Preliminary results show a large temporal variation in flows and concentrations across both streams, with varying loads of lead, but a consistent zinc load in the smaller stream. Initial results from the synoptic sampling show flows consistent with the salt gauging carried out after the stream had been sampled. This research will determine the extent of unseen inflow and outflows upon metal pollution on the River Tywi and allow mitigation strategies to be evaluated.</p>

Advances in stable isotope tracer methodology part 2: new thoughts about an “old” method—measurement of whole body protein synthesis and breakdown in the fed state

Whole-body protein turnover (protein synthesis, breakdown, and net balance) model enables quantification of the response to a variety of circumstances, including the response to meal feeding. In the fed state, the whole-body protein turnover model requires taking account of the contribution of absorbed tracee to the observed total appearance of tracee in the peripheral blood (exogenous appearance, RaEXO). There are different approaches to estimating RaEXO. The use of an intrinsically labeled dietary protein is based on the overriding assumption that the appearance in the peripheral circulation of a tracer amino acid incorporated into a dietary protein is exactly proportional to the appearance of absorbed tracee. The bioavailability approach is based on the true ileal digestibility of the dietary protein and the irreversible loss of the tracee in the splanchnic bed via hydroxylation of the tracee (phenylalanine). Finally, RaEXO can be estimated as the increase above the basal rate of appearance of the tracee using traditional tracer dilution methodology. In this paper, we discuss the pros and cons of each approach and conclude that the bioavailability method is the least likely to introduce systematic errors and is therefore the preferable approach.

Choline Supplementation in Cystic Fibrosis—The Metabolic and Clinical Impact

Background: Choline is essential for the synthesis of liver phosphatidylcholine (PC), parenchymal maintenance, bile formation, and lipoprotein assembly to secrete triglycerides. In choline deficiency, the liver accretes choline/PC at the expense of lung tissue, thereby impairing pulmonary PC homoeostasis. In cystic fibrosis (CF), exocrine pancreas insufficiency results in impaired cleavage of bile PC and subsequent fecal choline loss. In these patients, the plasma choline concentration is low and correlates with lung function. We therefore investigated the effect of choline supplementation on plasma choline/PC concentration and metabolism, lung function, and liver fat. Methods: 10 adult male CF patients were recruited (11/2014–1/2016), and orally supplemented with 3 × 1 g choline chloride for 84 (84–91) days. Pre-/post-supplementation, patients were spiked with 3.6 mg/kg [methyl-D9]choline chloride to assess choline/PC metabolism. Mass spectrometry, spirometry, and hepatic nuclear resonance spectrometry served for analysis. Results: Supplementation increased plasma choline from 4.8 (4.1–6.2) µmol/L to 10.5 (8.5–15.5) µmol/L at d84 (p < 0.01). Whereas plasma PC concentration remained unchanged, D9-labeled PC was decreased (12.2 [10.5–18.3] µmol/L vs. 17.7 [15.5–22.4] µmol/L, p < 0.01), indicating D9-tracer dilution due to higher choline pools. Supplementation increased Forced Expiratory Volume in 1 second percent of predicted (ppFEV1) from 70.0 (50.9–74.8)% to 78.3 (60.1–83.9)% (p < 0.05), and decreased liver fat from 1.58 (0.37–8.82)% to 0.84 (0.56–1.17)% (p < 0.01). Plasma choline returned to baseline concentration within 60 h. Conclusions: Choline supplementation normalized plasma choline concentration and increased choline-containing PC precursor pools in adult CF patients. Improved lung function and decreased liver fat suggest that in CF correcting choline deficiency is clinically important. Choline supplementation of CF patients should be further investigated in randomized, placebo-controlled trials.