Maintaining the Quality of the MPFM Measurements over the Life of the Field Author: M.M. Zoainat (Mohamad Mah’d Zoainat)
Co-Author: Alexandre Martins
1. Abstract Accurate production and reliable flow measurements are essential for making intelligent decisions on oil and gas production wells. Reliable flow rates are important to determine the reserves, the economics of continued operations to evaluate projects to improve oil and gas production and/or reduce water production–either means to increase well profitability and reserves. In this area of production measurement, Multiphase Flowmeters play a major role and is far more complex, both in terms of hardware and in terms of fluid flow dynamics. The challenges, however are in the reliability of the equipment, operational costs and the remote monitoring capability. Despite its robustness, the quality of measurements from a multiphase Flowmeter is highly influenced by the validity of the following inputs. • • • •
PVT’s Composition variation. Fluids densities variations Validity/Quality of the empty pipe Calibration. Scale deposit.
The multiphase flowmeter of this particular interest uses dual energy gamma attenuation principles combined with a venturi mass flow rate measurement. Measurement of phase fractions are based on atomic principles and with the help of periodic maintenance schemes, accurate and reliable measurements can be achieved at. This paper will focus on the effect of the above said factors on MPFM well testing data from Saudi Aramco- Qatif field in order to understand and qualitatively validate the meter’s output. The paper also sheds light on the effects of incorrect PVT sets used for measurements and resulting uncertainties. Effects of wax and
scale deposits on the monolithic windows, that are present in the path of the nuclear measurements, are briefly discussed in this paper. 2. Introduction Multiphase flowmeter manufacturer’s have always claimed for the need of using good quality PVT data to assure acceptable metering performance. The application and performance of multiphase meters has been well documented through technical papers and industry forums, and after several years of development is maturing (Scheers 2004). Some multiphase measurement techniques can perform better, and the meters provide a more compact solution, than the traditional separation approach. Effects on multiphase flow measurements in Qatif field due to the following listed factors have been studied extensively and this exercise will prove valuable to understand the metering technology and understand the importance of setting the correct PVT information and time to time monitoring and maintenance of the MPFM. The factors that were studied are: Effects of Sulfur concentration variation Effects of density variation and input data quality Effects of H2S & NaCl (Salinity) concentration variation and composition variation Effects of CaCO3 and non stable scale deposition Effects of reference measurement quality