Application of Laboratory PVT Data to Reservoir Engineering Problems

Abstract

The paper summarizes the historical background of the pressure-volume-temperature analyses of reservoir fluids, the errors involved in both the sampling and testing of reservoir fluids, the type of information required of a PVT determination , and the field conditions that limit the application of anyone analysis. Particular emphasis is placed on the necessity for approximating as closely as possible the liberation sequence occurring in the producing formation, flow string, and surface separators. A combined differential and flash or "composite" liberation is suggested as the best means of approximating this liberation sequence. HISTORICAL BACKGROUND Petroleum reservoir engineering commonly is considered to be one of the newest fields of petroleum science, yet much work of a theoretical and intuitive nature was done many years before the modern techniques of reservoir analyses were developed. The period 1910-1924 saw considerable work in the field of reservoir behavior done by the U. S. Bureau of Mines. This work,,-" although entirely theoretical, pointed out the importance of gas in the recovery of oil from the reservoir. The statement by J. O. Lewis that 20 per cent or less of the oil References given at end of paper. originally in place in a pool was recovered from the ground under uncurtaiIed production conditions caused some operators to reexamine and modify their production methods. However, though these works showed methods of production that have subsequently resulted in greater oil recoveries, they in general went unnoticed, even though there was a fear that the nation's petroleum resources were being exhausted. The period 1924-1933 saw the industry take considerably more interest in reservoir behavior because of an unfounded fear of its inability to replace oil reserves, the possibility of government regulation, and the energy of one man, Henry L. Doherty. Doherty aroused heated discussions in the industry concerning conservation. To prove or disprove his theories the first experimental work on the reservoir behavior of petroleum was undertaken. The papers of Dow and Calkin: Beecher and Parkhurst,' and Mills and Heithecker9 are classics although their experimental procedures were crude. These papers proved that the properties of petroleum in the reservoir are quite dissimilar to the properties measured at the well head. Gas dissolved in the oil phase was recognized as having considerable importance as had been predicted by the earlier theorists. Slightly later Miller'· and his co-workers assembled the first text correlating all the known data on the reservoir behavior of petroleum and used these data to show the economic value of conservation. Quantitative application of pressure-volume-temperature analyses of reservoir fluids was given in the paper of Coleman, Wilde, and Moore"; this work showed that with sufficient laboratory and production data prediction of reser-vo;r behavior was possible. The refined sampling and labora-Vol. 198, 1953 PETROlEUM TRANSACTIONS, AIME