Diagnosing Horizontal Well Production in the Belridge Field with Downhole Video and Production Logs
Authors: Whittaker J.L. , Golich G.M. , Smolen J.J. 
Published: December 2007

Abstract
Due to the problems interpreting conventional production logs (i.e., spinner) in horizontal wells, a video camera was run along with conventional production logs to provide insight into well performance. The video log gave visual information about the fluid flow regime along a horizontal wellbore and fluid entry at each fracture stage. This valuable information significantly enhanced the interpretation of conventional production logs and showed the various and complex flow regimes that occur in horizontal wells. These are the first successful video logs obtained in horizontal wells. This paper presents the design changes that made it possible to successfully run the video logs, the procedures used to run the logs in rod pump wells, and the results obtained from both the video and conventional production logging tools. It is beyond the scope of this paper to discuss the implications the results may have on future horizontal well completions.

Introduction
Production logging combined with downhole video logging provided significant insight into the production characteristics of three horizontal wells completed with multi-stage hydraulic fracture treatments in the diatomite reservoir of the South Belridge Field of California. Conventional production logging tools (PL) are difficult to evaluate in horizontal wells due to very complex flow regimes that can rapidly change along the wellbore. Although PL logs alone have been successful in evaluating horizontal wells, the video camera was included in this project in an attempt to provide visual information about the flow regimes and fluid entries. This paper presents the design changes that made it possible to successfully run the video logs, the procedures used to run the logs in rod pump wells and the results obtained from both the video and conventional production logging tools.
The Belridge oil field (Fig. 1) located about 40 miles west of Bakersfield California, is one of the larger producing fields in the United States, containing over three billion barrels of oil-in-place in a diatomite column greater than 1000 foot thick and extending over five square miles. The low permeability (&lt;1 mD) diatomite requires application of massive hydraulic fracture stimulation to obtain economic production. This horizontal well project was initiated in December 1995 to provide insight into the cost, productivity and technical aspects of applying massive hydraulic fracture stimulation technology to horizontal wells in the diatomite. Productivity of the horizontal wells was expected to be about the same as analog vertical wells but the actual productivity was only 50% of expected.
Fig. 2 shows the mechanical diagram of the horizontal well completions. (The second tubing string was not initially installed until production logging commenced as explained further in the paper.) Each well was drilled with the same medium bend radius (120/100 ft.) to accommodate conventional completion equipment. A 9–5/8" casing string was set and cemented after the well path reached 900 deviation. After reaching total measured depth, a 5–1/2" liner was cemented in place. The wells were then completed in stages (8–9) by perforating one foot intervals spaced every +/- 200 feet followed by massive hydraulic fracture treatments. The wells were then placed on rod pump. After the initial production rates were found significantly less than expected, a production logging program was designed to investigate the poor performance.

Production Logging Tool Selection
The production logging tools consisted of conventional 1–11/16 inch O.D., basket flowmeter, radioactive tracer, noise, nuclear fluid density, capacitance, Amerada pressure gauge, and a temperature probe. Appendix - PL Equipment gives additional basic information for readers not familiar with PL tools. Although new technologies exist for horizontal well production logging, conventional tools were considered adequate since the fluid entries would occur at a point source (1 foot interval) spaced up to 200 feet apart.
P. 337^