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The design and interpretation of an interference test for determination of formation compressibility in an offshore waterflood is presented. Interference well testing resolves some of the limitations posed by laboratory measurements of formation compressibility, i.e. the sample size is bigger, measurements are made in-situ and the method can be applied reliably in unconsolidated formations. Analytical and numerical PTA (Pressure Transient Analysis) models were used to select the active and observation wells and to design the interference test in terms of lag and lead times associated with the opening and closing of these wells. Some neighboring wells remained on production in between active and observation wells while the interference test was performed due to production constraints. This led to the challenge of unravelling the interference signal from the noise of continued production. Permanent downhole gauge data were utilized in seeking out the interference response at the observation well. Once the interference response was identified, the storativity (porosity-total compressibility product) was determined using the flow capacity (permeability-thickness product) calculated from the pressure and rate history at the active and observation wells. Formation compressibility was then calculated using log derived porosity values. Interference test analysis showed that the formation compressibility was significantly smaller than the pre-test estimates from the lab. The analysis resulted in narrowing of the uncertainty around formation compressibility that was later utilized in field production forecasts. Presence of high frequency high resolution data was critical in deciphering the interference signal. The breakthroughs came by using a range of the calculated flow capacity and total fluid compressibility in determining in-situ formation compressibility, which was in line with an offset analog field that had reliable laboratory measurements. The major impact of this work is in proposing a method for determination of formation compressibility in complex reservoirs and production systems from interference well tests utilizing permanent downhole gauge data.

This review work summarised new generation logging techniques such Tough Logging Conditions (TLC) & Logging While Fishing (LWF) and their advancement in drilling operations. The production of Oil & gas from the stage of exploration to production should need a lot of data for economic and safe operations. The conditions of the sub-surface cannot be simply predicted unless with some measured parameters under the LOGGING term. Logging is defined as a continuous record of Petro’s physical parameters of rock against time and depth. Instead of conventional logging techniques of wireline such as SP, Gamma-ray, Neutron, Calliper log, etc, logging while drilling, logging while fishing set them aside of their extended applications. Logging while Fishing is a new generation technology that allows unfailing operations of logging tool by a special installation even in cut and thread operation also aids economic and time enhancement. Tough logging conditions are a technique applied either when the hole has highly deviated or when you need to control the position of a tool. This project includes the study and interpretation of above discussed new generation logs. These tools offer all types of logging carried out on wireline except the SP logging. Logging while drilling provides real-time measurements of physical parameters while drilling operation itself which avoids an additional running of tools causing trips and sticking of drill pipe. The data is stored in the bottom assembled logging tool.