Knowledge Discovery in Databases and Multiphase Flow Metering: The Integration of Statistics, Data Mining, Neural Networks, Fuzzy Logic, and Ad Hoc Flow Measurements Towards Well Monitoring and Diagnosis

Abstract

Abstract The usual approach to the interpretation of producing wells is based on mechanistic models for the simulation of steady state and transient flow regimes. However, there are significant reservations about convergence problems, computational limits, the need for extensive tuning on field data, the instability of boundary conditions, the limited applicability of existing multiphase flow models, and the uncertainties associated with choke valve models. The current industry standards are critically reviewed within this framework. The real-time monitoring of producing wells is recognised as the best way of optimising field performance. Monitoring a producing well implies the ability to track, in real-time, any changes in fluid composition, flow rates, or pressure and temperature profiles. Multiphase Flow Metering (MFM) plays a key role in this scenario. Such information, combined with the critical analysis of historical data from the well itself or from analogue wells, allows diagnosis of the system and prediction of future trends. However, field data per se' do not necessarily generate knowledge. This is particularly true for large databases, which are difficult to manipulate to provide suitable inputs for wellbore simulators. This paper suggests how MFM, Knowledge Discovery in Databases (KDD) and Fuzzy Logic (FL) can offer an alternative approach to the analysis of producing wells. KDD is the automated extraction of patterns representing knowledge implicitly stored in large information repositories. Distributed, ad-hoc field measurements (including MFM and downhole measurements) can be processed via data cleaning, data integration, data mining, artificial intelligence, and pattern evaluation. FL can then manage the resulting information in terms of flow assurance and production optimisation. The same techniques can also be extended to the reservoir and the production network, for an integrated approach to production system analysis. Introduction Production wells are the physical connection between the reservoir and the surface facilities. As such, they are part of a production system, which is a network of components through which underground hydrocarbons must flow in order to reach the surface. It includes and is characterised by the following:the reservoir, with its geological and petrophysical properties, and also the properties of the fluids stored within it;the production wells, in particular, their completions and any artificial lift solutions;the flow control valves, such as the wellhead chokes;the flowlines, and any flow assurance solutions associated with them (such as single or multiphase pumping, thermal isolation and chemical injection);the separation and treatment facilities, both subsea and at surface. Beside this hardware, the properties of multiphase flows within the reservoir and through the production network must also be taken into account for the production system to be fully characterised. It is common knowledge that variations of any of the above characteristics are reflected in the rest of the system, and therefore that none of the elements of the system can be considered physically disconnected from the others. This means that the production system can be regarded as an integrated production system.