Flow Unit Thickness and Permeability Evaluation in Horizontal Wells Using Logging While Drilling and Wireline Formation Tester Transient Data

摘要

Oil was discovered in a carbonate reservoir which indicated discontinuous and complex geological features. The carbonate field in the Sultanate of Oman is at the early stages of development and reservoir uncertainties are still significant. The uncertain geological features, proximity of possible faults and heterogeneous reservoir properties make horizontal well placement a difficult task. The latest logging while drilling (LWD) technology for well placement was utilized to track the distance to the upper flow unit of the reservoir. It was discovered that the formation was dipping upwards and had separate units. The lower flow unit boundary was uncertain due to the LWD distance detection limit. Flow unit thickness identification became an important task to understand the potential of the reservoir. The objective of this study in the complex reservoir is to present a new way to determine the flow unit thicknesses by utilizing the LWD and wireline formation tester (WFT) interval pressure transient tests (IPTT) data. IPTT tests with a dual inflatable packer in combination with LWD logs resulted in local horizontal and vertical permeabilities and flow unit thicknesses along the horizontal well. Integration of the two distinct logging methods helped accomplish not only the well geometry and local petrophysical properties, but also gave information on large scale properties. The wells were also surveyed with open hole logging tools to obtain sedimentary features, to collect necessary oil samples and to obtain reservoir properties such as faults information, saturations, permeabilities and in-situ rock stresses. Following data acquisition and joint evaluation, an integrated study was conducted for the field development. This paper presents an integrated solution of LWD logs and IPTT data evaluation. The approach had a considerable impact on field development plans and reserve calculations in the new and complex carbonate reservoir.