Recovery Of Crude Oil By Nitrogen Illljectionlaboratory Displacement Data

Abstract

Abstract Four series of slim tube displacement tests were carried out on a Nisku crude oil at 103 °C, wherein the injection gases were nitrogen and nitrogen enriched with propane and carbon dioxide. Ail the runs were immiscible at pressures up to 34.6 MPa. Twelve floods were performed in Berea cores using the same oil to examine the effects of miscibility, water saturation, mode of injection, and care orientation. The propane slug/nitrogen chase gas mode of injection was the most efficient way of utilizing these gases to produce oil, especially when gas injection was carried out as a secondary enhanced oil recovery process. Introduction This is the second paper written by the authors (Sayegh and Wang) on the recovery of crude oil by N2 injection. The first Paper(l) dealt with the screening of petroleum reservoirs to select candidates for N2 flooding; phase behaviour data of a Nisku crude oil with N2, N2 plus CO2, and N2 plus C3Hg; and the correlation of the phase behaviour data using the Peng-Robinson equation of state. This paper deals with the displacement of Nisku crude oil from porous media by N2 injection, and includes slim tube displacement tests and their numerical simulation as well as Berea core floods. The oil-in-place (live Nisku crude), the injection gases (N2, CJHg and CO2 mixtures), and the temperature (l03 °C) are the same as those for the phase behaviour measurements. Table 1 lists some of the main properties of the live Nisku crude. The displacement pressures include those at which the phase behaviour measurements were carried out, as well as higher values. Hence, this paper, together with the work presented in Reference 1, provide complementary sets of data relating to the recovery of crude oil from petroleum reservoirs by N2 injection. Slim tube Displacement Tests of Nisku Crude Oil by N2 Mixtures The phase behaviour measurements presented in Reference 1 were designed to simulate the multiple contact process that occurs during oil displacement in porous media. A lot of information was gleaned from these measurements, but unfortunately only four "contacts" could be carried out because of equipment limitations. The slim tube displacement data presented in this section provide information on what occurs in such systems when a large number of contacts occur. Experimental Apparatus and Procedure The slim tube displacement apparatus is shown schematically in Figure 1, and a detailed description may be found in Reference 2. The tube itself was made from stainless steel, was 12.2 m long, had an internal diameter of 4.57 mm, and was coiled. It was packed with 100 µm diameter glass beads to a porosity of 0.37. Its pore volume was measured to be 73.7 ml. Live Nisku crude was the oil-in-place in all the displacements, 103 °C was the test temperature, and the gas injection rate was kept at 2.5 ml/hr for all of the runs.