Applications of Vapor Recovery to Crude Oil Production
Authors: Evans G.B. , Nelson Ralph 
Published: December 2007

Introduction

Profitable conservation is the aim of the crude oil producer. Changing conditions in producing practices and market requirements producing practices and market requirements continue to open new areas of profit potential for analysis. This paper discusses the utilization of vapor recovery systems as a lease installation for an income potential through the recovery of salable hydrocarbon vapors from stock tanks or crude oil stabilization units.

In recent years production practices, such as commingling of leases, centralization of crude oil storage tanks, and field unitization, have caused the concentration of larger volumes of crude production at a centralized point. Such points of crude oil accumulation offer ideal locations for the economic analysis of vapor recovery systems to recover either the normal hydrocarbon vapors lost from storage tanks or the vapors from a crude oil stabilization facility. This increases potential income from crude oil gravity control and the recovery of normal stock-tank vapor weathering losses.

The availability of a gas sales outlet wit a favorable contractual payment schedule is a prerequisite for any profitable application, prerequisite for any profitable application, Most existing contracts provide for payments of 25 to 40 percent of the liquid content value on the quality of gas normally available from vapor recovery systems. In this area a system that yields 40 Mcf or more per day is within range of economic feasibility and should be analyzed. Many such installed systems have yielded a return of investment, including operating expenses, in 10 months or less.

The horsepower requirement [5 to 40 hp] and the desired operational characteristics of a vapor recovery system usually dictate the use of electric power for normal economics. Experience shows that properly designed rotary compressors offer certain advantages in the compression of sour, wet gas. Data in this paper have been compiled on this kind of unit. paper have been compiled on this kind of unit. These units should function unattended; therefore, the components should provide this operation with adequate safety devices to protect the entire system.

Accurately determining the volume of vapor available is one of the more difficult problems in the economic analysis of a vapor recovery system. The critical calculations can be made, and, in the case of a stabilization system where most variables are controlled, these calculations are reasonably accurate. Because the determination of stock-tank vapors by calculations are subject to so many variables, however, it is necessary actually to measure for verification. Such measuring should be done under normal operating conditions over a period of 24 hours or more. A low-range period of 24 hours or more. A low-range recording manometer with an orifice well tester can be used for this purpose—rental units are available in several areas—but extreme care must be exercised to eliminate vapor losses at hatches and other points so that the total vapor volume available is measured.

The required delivery pressure of the compressed vapors should be determined carefully to meet both present and future requirements. Both the compressor capacity and horsepower of the prime mover are functions of this delivery pressure. pressure.

STOCK-TANK SYSTEM

To maintain efficiency and to meet the normal requirement of a gas purchaser, a vapor recovery unit on stock tanks must operate as a closed system under known and controllable conditions. The installation of such a system can be made with minimum renovation of the existing stock tanks.