Water Cut Estimation Using ESP Sensor Reading and Well Test Data: A Novel Approach
Authors: Sumarto Brahmantiyo Aji , Nugroho Bogi Haryo , Akbar Bibi Hussain , Al-Aradi Huda Jassim , Joenaedy Muhammad Arief , Achmad Pajar Rachman , Hakim Zainal 
Published: October 2022

Abstract

Objective/scope
Water cut is one of the critical parameters for production optimization and reservoir management in the field development area. Since the frequency of this well test is very limited, in terms of number in a yearly basis, there are gaps of time where do not have complete information on how much value the water cut (WC) behavior has changed. For an ESP well with excellent and stable behavior, petroleum engineer can still assume and predict the rates and WC performances are the same based on the last well test. However, for wells with unstable behavior, with its fluctuations in pressure downhole readings, this becomes a challenging task to monitor and estimate water cuts and minimize oil loss.
The flowing pressures in a well are represented, with typical pressure traverses in the tubing string and the casing-tubing annulus. Liquid gradient in a particular setting can determine the density of the liquid and the water cut in the flowing tubing. Most wells with low gas production rates produce wet oil, and the tubing contains an oil-water mixture. In this regime, the oil gradient change to the liquid gradient. Since liquid gradient in a particular setting represents can determine the density of the liquid and the water cut in the flowing tubing.
This paper presents a novel method to predict water cut in KOC’s North Kuwait New Field Development North Kuwait (NFD-NK) wells. By utilizing ESP downhole sensor and well test data, so that petroleum engineer understands the WC behavior of their wells better and be able to monitor and anticipate if there are any rapid changes in the WC behavior and perform actions to minimize oil loss. The model has been tested, showed consistently, and satisfactory results.

Method, procedure, process
A daily ESP sensor data reading is stored and available in the KOC system. PGOR or Well test job is typically performed 3 - 4 times/year to measure the production rates. Many parameters recorded and tested include a percentage of water production (WC). By utilizing continuous daily discharge pressure (Pd) readings from the ESP sensor and combined with well test data (flow rates and WHP), the WC value can be estimated as a function of a fluid gradient. Therefore, the model can obtain continuous WC trends over a long investigation period.

Results, observations, conclusions
The model is developed from a calculated fluid gradient and actual water cut from the well test as a validator. The linear model for each fluid regime is classified into low, medium, and high water cut. Each fluid regime WC has a different slope/m and can be used to estimate water cut along changes in fluid gradient. In most cases, indicate medium (50%) to high WC show minimal change of slope. It represents that the model is consistent and can be used to estimate water cut along changes in fluid gradient. Moreover, the model indicates satisfying results to confirm that the result validates to produced water salinity.

Novel/additive information
An alternative method to estimate water cut, the conceptual approach demonstrates a good agreement relationship between ESP sensor data to calculate water cut with high confidence. This method will be helpful to have actual water cut estimation. An advanced predictive analytic process turns traditional effort into an advance and scalable data-driven approach.