Stimulation Methods in Naturally Fractured Carbonates
Research output: Thesis › Master's Thesis
Stimulation of carbonate reservoirs is considered a routine operation. However, the presence of natural fractures makes the process more challenging due to several reasons such as fast acid spending rates, high leak-off and non-effective diversion. As it is the target to reduce the skin factor to the lowest possible value in each zone of the treated section the stimulation job must be carefully designed and optimized. Several kinds of diversion methods have been developed in order to uniformly cover the formation with acid. Those include chemical diversion techniques that alter the viscosity of the acid system, which reduces the entering of the acid into highly permeable zones such as fractures and subsequently redirecting the acid into less permeable regions. This guarantees that the stimulation fluids contact the largest possible reservoir surface area. Other stimulation techniques hydraulically fracture the formation in order to open closed natural fractures or to create new ones that connect the existing fractures leading to a more complex fracture network. Common techniques include acid fracturing and propped fracturing of rocks. In performing such stimulation treatments it is always of highest importance to take special care on all HSSE standards. Before introducing such advanced stimulation treatments in a certain country it has to be checked whether those treatments are in accordance with the local regulations. It is important to take such research into consideration but this is not the main focus of my thesis. In this thesis a worldwide case study on stimulation in naturally fractured carbonates is conducted. Afterwards it is compared with the stimulation of naturally fractured carbonates in Austria by OMV and observations and suggestions what to improve are illustrated.