An Innovative Approach Towards Improving Pressure Transient Analysis for a Tight Oil Formation: A Case Study

Abstract

Abstract As the oil industry matures, the development of marginal oil fields is becoming increasingly important. With the right technology, strategies and expertise, these fields can be unlocked to provide a valuable source of energy. The integrated application of the latest oil field technology and strategies has helped to make such development not only technically feasible, but also economically attractive. The appraising of highly faulted and tight carbonate formations has been a major challenge that requires an intelligently designed data gathering program and analysis. Additionally, due to the tight nature and heterogeneity of such formations, several pilot pressure transient activities end up being terminated, as the wells cannot flow naturally. This paper will present an innovative approach that was specifically tailored to enhance the quality of the recorded pressure data and understand and characterize these tight hydrocarbons. Presented in this paper is a smart and tailored workflow that was developed to record a representative pressure transient response in Abu Dhabi most challenging formation. A pilot well was selected for implementing this new testing methodology, the well suffered to produce naturally, multiple stimulation cycles were conducted, and the produced dead oil was re-injected again into the formation to record the pressure fall-off (PFO). During the analysis, deconvolution, which is a mathematical algorithm, was used to smoothen non-uniform injection rate data. The non-uniform injection rate data was a result of the poor quality of the formation, which did not tolerate higher injection pressure that might fracture the formation. The results show that the performed multiple acid simulations resulted in injectivity enhancements due to near wellbore properties improvements. Subsequently, this aided in the injection of a substantial volume of dead oil, amounting to hundreds of dead oil barrels into the formation, which was followed by a 10-day pressure fall-off test. This led to a further enhancement in the quality of the recorded pressure data compared to the conventional approach that was being used before. Additionally, the deconvolution algorithm implemented resulted in the enhancement of the pressure response during the injection period, which yields to improvement of the interpretation of PFO when compared to the conventional method. Moreover, the pressure data of an existing conventional well which records the pressure build up instantly before losing the prime pressure was compared with the well that is currently operating using the proposed approach. This approach allows us to obtain conclusive reservoir characteristics, which are always controversy. This innovative smart approach can be implemented as a common practice in the appraisal stage for tight and challenging formations, where the water or dead oil can be utilized as an injection fluid to obtain relatively stable rate thus reducing the number of the indecisive Pressure Transient Analysis (PTA).