SPE71075

Copyright 2001, Society of Petroleum Engineers Inc.

This paper was prepared for presentation at the SPE Rocky Mountain Petroleum Technology Conference held in Keystone, Colorado, 21–23 May 2001.

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Abstract

PGDBK Technology is used for the stimulation of oil and gas wells to enhance productivity. The pulsating pressure generated upon combustion of caseless cylindrical powdered charges overcomes the tensile strength of formation rock to create multiple fractures1. These fractures, with horizontal and vertical orientation, extend more than 100 feet in diameter from the wellbore. Combustion of PGDBK generators takes place near a selected pay zone in a well under a hydrostatic column sustained by a tamp fluid.

Through a combined effect of mechanical, thermal, and chemical actions, the use of PGDBK increases pressure communication between the extended reservoir and the wellbore. The pressure pulsating action of generated non-combustible gases erodes fracture walls keeping the flow channels opened for a long period of time without propping agents. High temperature generated through the combustion process cleans the wellbore region of heavy hydrocarbons, reduce the viscosity of oil and enhance relative permeability of oil to water. Additional oil is also recovered through the reduction of the surface tension by the chemical actions of the combustion products.

The in-situ process ends with a negative pressure gradient towards to the wellbore, washing impediments from flow channels. Wells are immediately swabbed or circulated to remove debris, equipment re-installed, and well brought back on line.

This paper describes the PGDBK stimulation technology. It further presents case studies of successful field applications in three different USA sedimentary basins in the summer of 2000 and recent treatments in Russia.Introduction

In the summer of 2000, GEOTEC Thermal Generators in collaboration with Federal Research & Production Center “ALTAI” (Russia) introduced the treatment of oil and gas wells in three different basins in the USA. Twenty wells were treated in the Powder River Basin, Anadarko Basin, and the Austin Chalk Trend.

Caseless charge-powdered pressure generators (in Russian – Poroxovie Generatorie Davlenea BesKorpusnie -PGDBK) have been effectively, safely and economically

applied in over 30,000 wells around the world to increase productivity. This is a state of the art stimulation technology that enhances the productivity of wells with a combination of mechanical, thermal, and chemical actions. The gas generated acts on reservoir rocks by creating multiple fractures that enhance the flow of oil and gas from the reservoir into wellbore1 (see Figure 1). These fractures are far-reaching and long lasting. They contribute significantly in reducing skin effect and increasing the permeability of the wellbore region.

The decline in a well’s productivity may largely be

attributed to deterioration of flow properties around the wellbore region. The flow channels are usually obstructed with formation fines, sediments of heavy-end hydrocarbons and contaminants from external fluids and materials during drilling and production. If no remedial action is taken to clear the flow channels larger pressure drawdown will be required to sustain production. This will cause the movement of more formation fines thus exacerbating the wellbore damage effect.

The most effective way to improve the flow properties of reservoir rock is to create fractures around wellbore. This improves hydrodynamic communication between the wellbore and the deeper region of the reservoir. Conventionally, fractures are created by hydraulic fracture, and acid fracture techniques. These are usually expensive and create only single fractures along least stress planes.

The PGDBK powdered gas pressure generators have been used successfully to create desired multiple fractures around the wellbore. Some of the advantages of this technology are the simplicity of its application, high mobility, less downtime, and minimal cost of personnel, equipment, and other resources. The PGDBK technology is applicable to diverse

geological, technical, and climatic field conditions.