Production Optimization of Oil Wells (the Problem of Salt Deposits)
Authors: Boussa M. , Bencherif D. , Hamza S. , Khodja M. 
Published: March 2010

The Hassi R'mel field is a gas condensate reservoir with a rather significant oil rim on the eastern and southern peripheries. Producing wells were confronted by a severe salt deposit problem, more or less related to the exploitation regime, which severely reduced oil production or caused the well to shut in totally.

The presence of sodium chloride inorganic precipitate in the well is undoubtedly influenced by:The type and quantity o water influx;Operating procedure; and,Reservoir characteristics, such as temperature and pressure.

A permanent fresh water injection under a packer did not improve the performance of these wells. A large volume of water injection is required for particular wells, tubing intervention. This treatment tends to become a cost factor and these wells are then shut in.

A study was undertaken in collaboration with the Research and Development Centre (CRD) at Sonatrach to solve the salt deposit problem in production due to the effect of temperature change. It consists of analyzing a sample of the formation water in order to understand the phenomenon of the salt deposit, to test the anti-deposition product efficiency, and to optimize its concentration under surface and bottom conditions, keeping in mind the reduction of the amount of injection water. Laboratory testing was undertaken first of all, in order to assess chemical water injection compatibility with formation water to ensure that the two fluids will not produce precipitates. It has shown that the alkylamide aqueous solution is used to prevent precipitation of sodium chloride crystals from high chloride brines from the bottom of the hole, changing crystal growth from symmetrical cubic orientation to a non-symmetrical dentritic type. Independently of entation to a non-symmetrical dentritic type. Independently of the temperature, its efficiency will also depend on the presence of other salts in the brine and the pH.

The purpose of this paper is to show:The problem created by sodium chlorite salt deposits which impede the performance of a well; and,Solution adopted to improve the Productivity Index, by using chemicals to reduce deposits of salt.

Introduction

The Hassi R'mel field demonstrates well performance problems due to salt deposits. During production, when the temperature in the tubings charges, water cools abruptly and salt deposit are formed(1).

Several studies were carried out to remedy and reduce these deposits of salts. In this study, we want to further examine methods to treat salt deposits in oil well production.

The Hassi R'mel field is a gas condensate reservoir located 500 km south of Algiers. The field extends 80 km from north to south and 60 km from east to west, with a rather significant oil rim in the eastern and southern peripheries(Figure 1).

The significance of the oil rim was highlighted with the drilling of well 8, which confirmed the existence of a significant accumulation of oil with good petrophysical characteristics and a great extention.

The first producing well was drilled in 1979, and encountered a series of sandstone at an approximate depth of 2,200m.