Pioneer in Integrated Workflow for Deep Transient Testing (DTT) from Interpretation to Forecast
Authors: Ratawessanun Watanapong , Hamdan Kamal , Ling Dennis , Daungkaew Saifon , Gisolf Adriaan , Millot Pascal , Cavalleri Chiara , Gao Bei 
Published: February 2023

Mini-DST, as alternative to conventional DST, has been in the industry more than 30 years, and its economic value has showed the advantage over DST, however limited permeability-thickness and investigated radius is a bottle neck which in many cases has much uncertainty to support reservoir characterization. The recently developed Deep Transient Testing technology improved its performance over former mini-DST technology in terms of longer pumping time, larger produced volume, and greater investigation radius. This paper presents a study in a variety of environments and applications, demonstrating how formation testing is being planned, acquired, and used in new ways, including Deep Transient Testing (DTT). The comprehensive radial model approach based on DTT using integration of well logs, numerical simulation grid and pressure transient behavior is built for the first time.

To design an effective approach to generate a radially gridded single well predictive model, this workflow requires knowledge of well performance, petrophysics and reservoir simulation. This simulation workflow started with a petrophysical interpretation together with well surveys which serve as essential input data to build a single well predictive model. Rock typing using Heterogenous Rock Analysis (HRA) method resulted in a more detailed properties population along the vertical direction in tartan grid. Defining completions of the well and followed by conversion of tartan grid to radial grid was performed to accurately capture the pressure transient response near wellbore. The radial grid model was setup as a DTT model to forecast the pressure transient behavior of the reservoir incorporating the technology of a new intelligent wireline formation testing platform in the simulation inputs.

The outcome of this study produced multiple scenarios incorporating different reservoir tightness from low to high with known thickness. The reason is that as the formation gets tighter; it is more challenging to achieve radial flow and predict producibility. By having uncertainty study in place, we can understand the outcome of each scenario then provide quantitative data to make decision on DTT feasibility, inlet and flow manager selections based on simulation result. This methodology not only optimizes the operation planning and execution, but also estimates pressure drop and the time needed to be on stationary for operational risk mitigation, which are in place to help operators improve certainty in decision making.

The case study showed that the advanced 3D radial grid predictive model method addressed the advantage of Interval Pressure Transient Testing (IPTT) and DTT in accessing and evaluating reservoir connectivity, heterogeneity, and drainage radius. In this paper, we are the pioneer in this robust Intelligent FT integrated workflow globally, which was successfully implemented together with all wireline operations within planned time frame involved and delivered with exceptional results.