Analysis of the impact of reservoir fluids invasion on well performance and productivity.

International Journal of Research and Innovation in Applied Science (IJRIAS) | Volume VII, Issue I, January 2022 | ISSN 2454–6194

Analysis of the impact of reservoir fluids invasion on well performance and productivity.

¹Precious Chisom Jumbo-Egwurugwu; ²Franklin Okoro; ³Obo-Obaa Elera Njiran
^1,3 University of Port Harcort
² CleanScript Group

ABSTRACT
This paper assessed the impact of fluid invasion on well performance and productivity. OLGA simulation of fluid invasion into the well was done to generate data points for modelling the effect of fluid invasion on well performance and productivity. From the simulations, about 32 data points were generated which were exported to excel and was analyzed using data analysis toolpak. The outcome of the analysis generated a multi variate correlation which equated well performance in terms of volume flow rate to independent variables including the tubing total fluid content in the well. The trend volumetric plots from OLGA were used to indicate the onset of fluid invasion into the well and for this study, the critical volume flow prior to the onset of fluid invasion was 450,000 sm3/day and this occurred after about 38 hours of flow. The implication of this is that, below this rate, the well is underperforming due to fluid invasion and the continuous experience of fluid invasion will later cause a total formation damage, and when this occurs, the production is completely interrupted. The correlation revealed that the relationship between fluid content in the wellbore and the well productivity is inverse. That is, a decrease in fluid content in the wellbore results to an increase in the well productivity. With this correlation, at any point in time t, the well productivity can be predicted and from the value of the volume flow rate of the well, it can be confirmed if the wellbore is underperforming due to fluid invasion or not. The correlation was validated using statistical analysis by assessing the R square, P, Significance F values and the trend plots of the predicted volume flow rates and actual volume flow rates. These tests confirmed that the correlation is statistically significant.

Keywords: Fluids’ invasion; Well performance; Well productivity; OLGA; Reservoir.

INTRODUCTION

During well construction, drilling fluids are used to control the borehole pressure, to reduce the temperature of the drill bits and to circulate the drilled cuttings out of the boreholes. Drilling fluids need to be carefully designed so that they can have certain density and viscosity to maintain the wellbore stability and lift the cuttings (Xiaoyan, 2011). To obtain the required viscosity and density, various solid particles are added to drilling fluids. Besides these solids, drilling fluids also contain cuttings which are generated during the drilling process. Because of the pressure difference between the wellbore and the formation, drilling fluids flow into the permeable formation (Fakoya and Ahmed, 2018). Consequently, the suspended particles in the fluids penetrate into the formation matrix under the action of the hydrodynamic drag forces exerted by the fluids, and then are gradually deposited on the formation grain faces drilling particles penetrate into the formation matrix and are deposited in the near wellbore region (Elkatatny et al., 2016). The invaded particles reduce the porosity of the formation, impair the formation permeability, and thus adversely affect the productivity of the well (Adam, 2017).
Invasion of solids fluid and formation that can lead to particle plugging or fine migration is also another serious concern of formation damage. The measure of formation damage is called “skin” (Omotara et al., 2015). The formation damage obviously reduces well deliverability, drainage efficiency and ultimate recovery (Elkatatny et al., 2013) (see Figure A). These parameters are key factors to determine the reservoir performance and field development, production test, pressure build-up test or drawdown test indicates formation damage (Okotie et al., 2015). Thus, this paper analyzed how the invasion of fluids into reservoir affects well performance and productivity.

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