Late Life Field Management with Instrumentation Failure. Modelling Predictions and Successful Validations of Late Life Subsea Gas Condensate System Using Historical Field Data

Depleting reservoir pressure, increasing water cut and decreasing overall system production leading to increased liquid holdup are among the key challenges for typical late life gas condensate production system. This paper elucidates modelling details of a late life offshore subsea gas condensate system and how the findings are implemented and validated with actual field data for successful outcomes. There is only one subsea well remain in operation with relatively long subsea flowlines. Subsea pressure and temperature transducers are out of service as the asset approaches the end of design life. In this context, flow assurance team has taken the modelling approach in order to minimize cost and to maximize values. Detailed transient multiphase thermohydraulics models are developed and benchmarked against field data. Historical field data over the past two years are utilized in order to predict the trend for key parameters such as well production rates and water to gas ratio (WGR). Matrix of simulation including the predictions of slugging flow regimes are carried out for the entire flow path, from reservoir characteristics descriptions at bottom hole, through flow regimes analysis at topsides slug catcher. Three categories of operation characteristics, namely the low risk, medium risk, and high risk production periods are identified. It is predicted that the system would start to fall into slugging flow regimes from 2 months onwards with final production end date of after 10 months. This is shared with wider team such that operations and base management teams are informed with predicted multiphase flow characteristics for the remaining production life. As such, gas supply succession plan can be executed in time to ensure uninterrupted downstream commercial agreement. Feedbacks from operations team revealed accurate predictions of such analysis, including slugging flow phenomenon which was associated with flow and pressure fluctuations, was observed in field as predicted by the study. More importantly, the production cut-off date is accurately predicted 10 months ahead and within the accuracy of ± 1 week. This study demonstrated how historical field data, coupled with detailed transient multiphase thermohydraulics modelling, can be utilized for offshore gas condensate production predictions during late life. Without transducers and/or virtual metering data feed, production end date can be accurately predicted based on key parameters analysis. This is particularly valuable for supply succession planning and is deemed a successful case study with significant positive outcomes which can be used as reference for other gas condensate assets.

An improved Wilson equation for phase equilibrium K values estimation

Phase equilibrium K values are either estimated with empirical correlations or rigorously calculated based on fugacity values determined from an equation of state. There have been several empirical analytical equations such as Raoult’s Law, the Hoffman Equations (Hoffman A, Crump J, Hocott C. Equilibrium constants for a gas condensate system. J Petrol Technol 1953;5:1–10) and their modifications and the well-known Wilson Equation (Wilson G. A modified Redlich–Kwong equation of state applicable to general physical data calculations. In: AIChE National Meeting Paper15C, May 4–7, Cleveland, OH; 1969). along with several modifications. This work presents a new modification of the Wilson Equation for estimating phase equilibrium K values, predominantly for light hydrocarbon mixtures. The modification is based on correlating a subset of a database of K values, established from convergence pressure data. Results show the method to accurately correlate and predict the K value data, within 10% on average. Moreover, the predicted K factors provide remarkable results for such a simple model when used in a variety of phase equilibrium calculations. The results also show that the new model compares favorably with existing empirical analytical methods. Such a model would provide excellent initial estimates for rigorous thermodynamic calculations.

Studying the impact of carbon dioxide on phase transitions of gas-condensate systems and dispersion of retrograde condensate

The paper studies the effect of carbon dioxide on the phase transitions within gas-condensate systems and defines its role on the evaporation of retrograde condensate isolated in formation due to the decreasing pressure during development process. Based on the experiments carried out by special methodology in рVT bomb, the essence of various impact of carbon dioxide amount in the content of gas-condensate mixture on the physico-chemical and thermo-dynamic parameters of the system depending on the temperature interval revealed. As a result of experiments, it was defined that the increase of carbon dioxide within gas-condensate mixture raises the content of dispersed condensate in gas phase. Moreover, the increase of CO2 in gas phase leads to the growth of gas amount dissolved in a unit volume of condensate as well. It is shown that the effect of carbon dioxide on the pressure of retrograde condensation within gas-condensate system cannot be definitely estimated. The pressure of retrograde condensation within such mixtures may be different in various temperature diapasons due to the change of the features and critical parameters of the system.

Comparative analysis of the efficiency of optical and calorimetric methods for studying the near-critical state of hydrocarbon mixtures

By the example of a binary hydrocarbon methane–pentane mixture simulating the simplest gas-condensate system, it is shown that the optical method for studying the near-critical state of hydrocarbon fluid, using the measurement of the intensity of critical opalescence in the vicinity of the liquid–gas critical point, gives more accurate and reliable results for the dew–bubble curve and values of critical parameters of the fluid than classical adiabatic calorimetry, which uses the thermogram method to record the change in the phase state of the fluid in the near-critical region.

Synthetic protein condensates that recruit and release protein activity in living cells

Compartmentation of proteins into biomolecular condensates or membraneless organelles formed by phase separation is an emerging principle for the regulation of cellular processes. Creating synthetic condensates that accommodate specific intracellular proteins on demand would have various applications in chemical biology, cell engineering and synthetic biology. Here, we report the construction of synthetic protein condensates capable of recruiting and/or releasing proteins of interest in living mammalian cells in response to a small molecule or light. We first present chemogenetic protein-recruiting and -releasing condensates, which rapidly inhibited and activated signaling proteins, respectively. An optogenetic condensate system was successfully constructed that enables reversible release and sequestration of protein activity using light. This proof-of-principle work provides a new platform for chemogenetic and optogenetic control of protein activity in mammalian cells and represents a step towards tailor-made engineering of synthetic protein condensates with various functionalities.