Coil tubing conveyed production logs were obtained from four high angle and two horizontal wells in the Norman Wells oilfield during September 1990. Five wells were producers and one was an injection well.
Coil tubing systems have seen increasing use in the past five years due to an increase in horizontal and directionally drilled wells. The use of coil tubing has recently been expanded to include wellbore evaluation. Important data relating to fluid inflow into a horizontal wellbore can now be obtained by conveying production logging tools to and across hydrocarbon bearing zones on the end of coil tubing.
The Norman Wells oilfield is located in the Northwest Territories, Canada, 80 km south of the Arctic Circle (Figure 1). The reservoir is located in the Kee Scarp limestone reef which is Middle Devonian in age, equivalent to the Swan Hills formation reefs of Central Alberta. The Kee Scarp formation is divided into a number of markers which are characteristic of sea level controlled reef growth. The production mechanism is a horizontal water flood using five spot pattern configurations. Artificial lift for the producing wells is achieved by gas lift facilities. The surface facilities include 17 satellites located on three natural islands, six artificial islands and the mainland.
A large portion of the oilfield is located underneath the Mackenzie River (Figure 2), which spans a width of up to four kilometers at Norman Wells. Horizontal and high angle wells have been routinely used to access and exploit the reserves. Evaluation of the production profiles for these wells was not possible until the advent of coil tubing conveyed production logging practices.
Well deviations greater than sixty degrees present a unique problem for production profile determination. Conventional methods of lowering the logging tools down the wellbore cannot overcome frictional or drag forces of the tubing. Coil tubing with wireline spooled inside the tubing offers the opportunity to convey the tools down highly deviated or horizontal well bores. Figure 3 is a plot of true vertical depth versus horizontal displacement for the six wells that were logged.
A standard production logging program was designed for the five oil producers to be surveyed. The program was designed to locate and identity areas of water, oil and high gas-to-oil ratio (GOR) production. Previous production logging programs on vertical and moderately deviated well bores in this field indicated that low volume three phase flow would not be useful for obtaining data for a guantitative analysis of the flow profile.
The wells were surveyed under both flowing and static conditions. A minimum of two passes against the flow and one pass with the flow were performed for each of the two tool strings deployed down the well. Figures 4(a) and 4(b) represent the tool strings used to log the producing wells.
Logging speeds ranged from 6 m/min to 12 m/min. Station "stop-check" data was obtained at one meter intervals with the noise tool and between each set of perforations with all the tools.
