The Cement Slurry and Technology of the Cementing for Environments Abnormally High Content of Hydrogen Sulfide
Authors: Utkin Denis Anatolevich , Garshina Olga Vladimirovna , Kudimov Ivan Andreevich , Okromelidze Gennady Vladimirovich 
Published: September 2020

A large number of world hydrocarbon reserves are concentrated in fields with a high content of hydrogen sulfide. In the Russian Federation, according to the safety rules in the oil and gas industry, these are deposits that contain in their products more than 6% (volume) of hydrogen sulfide (Order of the Federal Service for Ecological, Technological and Nuclear Supervision of March 12, 2013 No. 101).

An analysis of field data and published works shows that customers suffer multimillion losses from well downtime due to behind the casing gas showings of hydrogen sulfide at the mouth and inter reservoir flows during development and operation. One of the reasons for such problems is a violation of the tightness of the lining of the well as a result of unsatisfactory quality of cementing, including due to the use of grouting materials that are not resistant to hydrogen sulfide aggression.

The creation of a tight support for a well under conditions of hydrogen sulfide aggression is a very difficult problem. Acting as a diffusion barrier for the penetration of formation fluids, cement stone prevents their direct contact with the casing. Under the influence of aggressive hydrogen sulfide environments in the cement stone, physicochemical processes occur that affect the stability of the metal of the casing strings protected by the cement ring. This causes the development of corrosion of their surface, which in turn reduces the overhaul period of the wells. This circumstance is unacceptable from the standpoint of industrial and environmental safety of the operation of hydrogen sulfide-containing deposits.

Both in Russia and abroad, the problem of cement corrosion is not given due attention. One of the reasons that the scale of research on longevity is inferior to the development of new formulations is the duration and high complexity of the first.

In addition, it is worth noting that currently there is no standardized test method for the resistance of cement stone to certain types of corrosion in specific thermobaric conditions of oil and gas wells and laboratory equipment with the possibility of modeling conditions.

A universal method of increasing the corrosion resistance of cements in any aggressive environment is to slow the diffusion of the latter deep into the products at the contact of the cement matrix and aggregate. It is possible to increase corrosion resistance due to the rational choice of a binder and the use of active aggregates that interact with the cement matrix of the initial binder by various mechanisms, which reduces the conductivity of the contact zone for aggressive components of the formation fluid.

The work is devoted to solving the problem of poor quality of cementing casing strings under conditions of high hydrogen sulfide content by improving the technology of fastening wells using developed cementing material resistant to hydrogen sulfide aggression, special buffer systems, and technical equipment.

Grouting material for cementing productive horizons with a high content of hydrogen sulfide (more than 6% by volume) was developed according to the results of theoretical and experimental studies.

To assess the resistance of the cement stone to H2S, developed a new technique, and comprehensive laboratory tests were conducted.

Cementing technology field tested.