Establishing Water Injection Dynamics by Leading-Edge Coreflood Testing (SPE-121786)

摘要

The increasing amounts of water being produced from oilfields, and the increasing need or necessity to return this water to the reservoir it originated from, are posing a challenge to the industry. A fundamental question in Produced Water Reinjection (PWRI) is: "How clean is clean ?", or perhaps even more succinct : "How clean is fit for purpose ?". There is no universal correct answer to this question, as it depends on specific variables, largely intrinsic properties of a reservoir, its produced fluids and its inherent contaminants. Whilst of limited relevance to water disposal, PWRI for reservoir management purposes must find the balance between injector plugging and the extent of induced fractures. Finding this balance ultimately weighs injection water quality (read : treatment system) against reservoir performance, an activity fraught with uncertainties. As the conventional view on mechanistic particulate plugging of permeable media is now considered invalid, due to chemistry and wettability related effects, it is opportune to resort to empirical techniques, such as coreflood tests. Many were undertaken over the last few decades, but unfortunately none sufficiently approximated actual injection practice, resulting in spurious results. Recognizing this, Shell developed a coreflood test rig, featuring accurate, automated high injection pressure capability and a much extended test duration, which overcame the flaws and pitfalls as inherent to contractor provided coreflood services. This test rig has now been field tested at two oilfields, main findings being : 1. Steady-state conditions can only be achieved in extended exposure windows 2. Leak-off dynamics at high dP cannot be extrapolated from experiments at low dP 3. Filtercake permeability depends on the permeability of the flooded core 4. Membrane tests (Barkman-Davidson) fail to give representative filtercake properties It is thought that the now gleaned information will provide much improved input for simulators modelling fractured injection.