Additional effects stem from pore angularity (3) differences in air-entrapment mechanisms and (4) swelling and shrinking of the soil under wetting and drying, respectively. The macroscopic manifestation of hysteresis in soil water retention (or soil water characteristic) is rooted in several microscale mechanisms, including: (1) differences in liquid–solid contact angles for advancing and receding water menisci ( Figure 14a), which is accentuated during drainage and wetting at different rates (2) the ‘ink bottle’ effect resulting from nonuniformity in shape and sizes of interconnected pores, as illustrated in Figure 14b, whereby drainage of the irregular pores is governed by the smaller pore radius r, and wetting is dependent on the larger radius R. This phenomenon, known as hysteresis, is closely related to various aspects of pore geometry, capillarity, and surface wettability. The amount of liquid retained in a porous medium is not uniquely defined by the value of the matric potential but is also dependent on the ‘history’ of wetting and drying. The data corrections used to process experimental data (closure and centrifuge end face saturation corrections) and capillary pressure data: stress, clay-bound water and IFT are described and explained. The advantages and drawbacks/issues associated with each test are described and quality control checks and diagnostics are summarised. This chapter describes the sample preparation methods, test equipment, test procedures and data reporting requirements for the principal drainage and imbibition capillary pressure tests using mercury injection (low and high pressure), porous plate, and centrifuge methods. Imbibition capillary pressure is used to describe reservoir fluid displacement processes on production and to interpret the results of relative permeability experiments. Accurate knowledge of the capillary pressure distribution on drainage is one of the primary factors in the reliable estimation of hydrocarbon reserves. Izaskun Zubizarreta, in Developments in Petroleum Science, 2015 AbstractĬapillary pressure in a reservoir determines the saturation distribution, and hence the total in-situ volumes of fluids (oil/water/gas).
0 kommentar(er)
