New Reagents for Development of Wells After Drilling Operations, Killing by Polymer Solutions and Hydraulic Reservoir Fracturing
A.P. Merkulov /OOO Zirax,
A.I. Мikov, A.I. Shipilov, V.A. Zhuravlev /CJSC POLYEX/
R.E. Zontov /ООО Gazprom Production Astrakhan/
А.П. Меркулов (ООО «Зиракс»),
А.И. Миков, А.И. Шипилов, В.А. Журавлёв
Р.Е. Зонтов (ООО «Газпром Добыча Астрахань»)
For already 10 years the company Zirax operates as a producer and seller of speciality chemicals for oilfield applications and industrial chemicals for a range of manufacturing industries.
The main directions of activity are elaboration and production of highly clean sparing liquids for wells killing on the basis of sodium, magnesium, calcium salts and acid compounds by utilizing synthetic hydrochloric acid to increase oil recovery and develop wells after drilling operations, killing and hydraulic reservoir fracturing.
The company’s main priority is the way from the demands of the market and the customers. Under the construction of oil and gas wells and the conduct of their major overhauls the polymer compounds are widely applied. The main operations with application of polymers are:
- Wells killing
- Water insulating operations
- Hydraulic reservoir fracturing
- Massive treatments of the bottomhole zone
Under wells’ capital repair the polymer compounds are applied for flow deviating or preventing from falling technological liquids in the collector. As polymer materials there are used both synthetic materials: polyacrylamides and their copolymers, and the polymers of natural origin: carboxymethyl cellulose, guar gum, starch and xanthane gum.
Alongside with obvious advantages of these materials, there is a number of problems connected with their negative impact on the bottomhole zone of formation and the decrease in filtration properties of the collector. The main reason consists in the fact that any polymer contains a solid phase which is potential colmatant. Besides, highviscosity gels under falling to the bottomhole zone of formation form a stable screen preventing the flow not only of water, but also of the hydrocarbon phase. Under drilling, the polymers are used to regulate the technological parameters of the drilling solution.
Along with them, various weighting compounds on the basis of clay or barite can be used. Such polymer clay solutions also can be a reason for mudding the bottomhole zones of formation, forming a cake of drilling solution on the rock of the collector. In this regard, under development of wells, after drilling it is needed after drilling to provide the destruction of cake in order to achieve the planned production level. Acid baths applied in some cases do not solve this problem because hydrochloric acid is poorly reacting both with polymers and with clays.
Therefore, urgent is the task of creating a complex reagent which is able to destroy the mudding screens formed by various polymer and polymer clay solutions. Together with the specialists of CJSC POLYEKS the research has been carried out and the manufacture of acid compounds on a commercial basis has been arranged allowing one to solve this task.
At the first stage, research was carried out with the aim to choose an optimal formula of the compound for efficient destruction of cake of the drilling solution. It is known that under filtration of the liquid drilling solution, practically a complete division of its phases occurs in the bottomhole zone of formation: filtrate (with the components dissolved in it) goes to the formation causing hydration under the presence of clay inclusions, while the filtered disperse hard phase with the arisen excess of concentration of clay particles, the polymer containing reagents and the residual watering of 30 %, forms a clay cake and muds the bottomhole zone of formation.
Therefore, to assess efficiency of the elaborated compound, a special method was used taking into account this mechanism of impact of the drilling solution on the bottomhole zone of formation. It was needed to prepare a clay solution modeling the most complicated system for destruction. Its compound is given in Tab. 1.
The batch of clay, 50 g, was added to the batch of ready solution, 50 g, and everything was thoroughly mixed up to dough-like consistence (with residual watering 30 33 %).
The prepared "dough" was placed into the desiccator and left for swelling during 3 -4 hours. Identical samples of spherical form of 4,0 g in weight were formed of ready "dough" directly prior to the conduct of research. The scheme of equipment for assessment of destruction dynamics of artificial sample is given in Fig. 1.