HODGES, J.W., MEMBER AIME, SUN OIL CO., BEAUMONT, TEX.
The constant search for methods to increase the efficiency of production systems and to reduce operating costs has led to the development of a wireline tool which makes it possible to produce and control two separate reservoirs through a single string of tubing. This paper is a progress report of the experience one company has gained with this tool in eight of its dually complete wells in Louisiana and Texas. Field tests have clearly demonstrated that this device can be used to maintain separation of production from each and to change the rate of production as required. The advantages in simultaneous one-string multiple completions of the method are discussed.
It is now almost standard operating procedure to complete wells in more than one zone wherever possible, with the great majority of these multiples being dual completions. This is a sign of the times. Saving must be accomplished wherever possible; however, there is no need to expand on this theme. All are painfully aware of the economic conditions within the industry. It is sufficient to say that the practice of multiple completions is here to stay and is becoming more popular every day. The only question is whether or not the practice has evolved into its most acceptable form. The earlier duals were the concentric type, with one zone producing through the tubing and the other through the tubing-casing annulus. This method is still practiced to a large degree. It is popular because it is relatively inexpensive. Unfortunately, it has some rather severe limitations, with which the reader undoubtedly is familiar. The twin-string dual is an improvement over the concentric in the sense that many of the problems associated with the concentric have been solved. The objectionable features of the twinstring dual are the high cost of equipping the well with an extra string of tubing, plus accessories, and the complications brought on by cramming all this tubing into one string of casing. Still another type of multiple is the tubingless completion, wherein two or more small casing strings are cemented in place and subsequent operations performed with miniaturized equipment. The purpose of this paper is to present a different concept in multiple completion-the simultaneous production of separate reservoirs in a single flow string. This method combines the simplicity and low cost of the concentric with the flexibility of the twinstring dual. In addition, it provides the unique advantage of prolonging natural flow from a low-pressure zone by combining its production with the fluids produced from a higher-pressure zone. The wireline tool which makes this method possible is the multiple-completion choke assembly.
Fig. 1 shows a well properly equipped to receive a multiple-completion choke assembly. A conventional packer separates the two producing zones. The upper packer is optional.