A new approach in pressure transient analysis part I: improved diagnosis of flow regimes in oil and gas wells

Abstract

This paper introduces the statistical method for diagnosing flow regimes for flowing and shut-in conditions. The method utilise the second differencing of pressure change and time that are stationary; then integrate the residual pressure differences using simple statistical tools such as sum of square error SSE, moving average MA and covariance of data to formulate the statistical derivative models. These models are tested with constant pressure, constant rate conditions and in well with high water production. Results from three scenarios investigated demonstrated that the statistical derivatives yielded much clearer reservoir radial flow regimes as the conventional pressure derivatives without data smoothing; therefore give more confident formation permeability estimation. It demonstrated that for high water production well, a good radial stabilisation can be identified. It also showed that in all three scenarios, the drawdown radial fingerprint can be replicated in the build-up pressure responses, hence a good match of the data.

Statistical and numerical density derivatives: example of flow regime diagnosis and permeability k estimation

“…3 depicts the expected density derivatives for each fluid phase generated from Horne (1995) and Biu and Zheng (2015).…”

“…or the statistical pressure derivative formulated by Biu and Zheng (2015), transformed into density form as follows:…”

“…This paper introduced the statistical and numerical density derivative developed from the fundamental of PTA which assumed that there is a small change in fluid-phase densities at the wellbore and the phases flow independently. In this study, the density derivatives from the DTA solution and pressure-density equivalent derivative are generated from Horne (1995) mathematical derivative equation or the new statistical derivative equation by Biu and Zheng (2015). The statistical and numerical density derivative serves as a support tool for better interpretation and estimation of reservoir properties in these conditions.…”