Abstract

In 1994 Texaco personnel viewed chemicals as the primary means to reduce water handling costs. They recognized from downhole videos that oil and water remain separated in the tubing-casing armulus Capitalizing on this revelation of "gravity segregation," they conceptualized a dual-ported, dual plunger rod pump to produce oil and water from the armulus on the upstroke while injecting water on the downstroke. Texaco and Dresser jointly developed this pump and named it the Dual Action Pumping System (DAPS). In January 1995, the first generation prototype was installed. It verified the technical and economic feasibility of this new technology. It substantially increased production while simultaneously reducing power requirements. A second generation prototype was developed to improve the valve design. It has continued to function without problems since its installation in October 1995. Tests in a Rocky Mountain Oilfield Testing Center well and several Talisman wells have further demonstrated that this will be a unique, new tool for the oil industry. This paper will both explain how DAPS works and describe some of the early testing results. Work is continuing to improve the performance predictions. Tests have shown it to be an inexpensive technology that can reduce lifting costs and thereby increase and/or accelerate reserves recovery when the right conditions exist. while many potential applications or benefits of DAPS have been identified, these can generally be classified in three categories:

  • Increase oil production

  • Reduce water handling costs

  • Reduce potential investment costs

Introduction

In 1993, many of Texaco's oil fields and wells were rapidly becoming uneconomic to produce because of excessive water production. Texaco's Exploration and Production Technology Division (EPTD) was requested to evaluate ways to manage excessive water production. This was conceived largely as a concerted attempt to use chemicals or cement to shut off excessive water. A surprising new option became apparent. Part of the process was to conduct a literature search and monitor industry activity in this arena. This monitoring revealed was that it is possible to utilize pumping units for tasks such as downhole injection, surface pumping, gas compression, and other purposes. The scope of the study also envisioned improved diagnostic procedures. One of the diagnostic tools evaluated by EPTD was the downhole video. Tapes provided by Halliburton Energy Services showed their tool had potential to qualitatively determine which perforations produce the most oil. With somewhat more difficulty, it appeared that perforations producing excessive amounts of water could also be identified. Texaco ran a downhole video in one of its wells that was equipped with a pumping unit, to test this latter theory.

Downhole Gravity Segregation.

Again, it was noticed from this video that the oil droplets were distinctly separate from the water that was being produced. This is unlike the murky mixture of oil and water typically seen at the surface. In fact, these distinct oil droplets literally squirted into the wellbore with each stroke of the pump. The rising oil droplets looked like the oil in a lava lamp. From this it was recognized that oil and water are typically separated by gravity segregation in the wellbore until they are mixed together by the pump. In retrospect, we realized that there is other evidence of this phenomenon. Consider a conventional rod pump in a high water-cut well that is pumping below the producing perforations. After it has been off production for several days, it may take hours or days before it starts producing oil again. This occurs because the oil has collected at the top of the armulus. P. 403^

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