Boring or penetrating the earth – Processes – Boring with specific fluid
Patent
1998-12-02
2000-11-21
Bagnell, David
Boring or penetrating the earth
Processes
Boring with specific fluid
166312, C09K 700, E21B 2100
Patent
active
061489328
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method and to a system intended for drilling and cleaning operations in underground working wells or for bringing in operations in the case of a reservoir. In the method, circulation between the ground surface and the well bottom and return to the surface are performed from a string of pipes lowered into the well. The foam is generally injected through the inside of the pipes and it returns through the annular space defined by the pipes and the walls of the well. The fluid in the form of foam carries the cuttings along to the surface, thus cleaning the wall face. This technique, referred to as foam drilling, is well-known and has notably the advantage of not generating too high a bottomhole pressure thanks to the low density of the foam. However, the main drawback of this technique is that it does not allow ready recycling of the foaming solution, in view of the products initially brought into solution to stabilize the foam after stirring and gas injection. <<Breaking >> of the foam is the basic problem if one wishes to recover most of the foaming products for repeated use, or if the environment conditions do not allow spreading of the volume of foam returning from the well.
Document WO-94/17,154 proposes using an amphoteric foaming agent combined with surfactants as the base for a stable foaming composition. The foam is broken by a suitable variation of the pH value of the foam. If the foam is basic, it is broken by decreasing the pH value at least below 4, and if the foam is acid, it is broken by raising the pH value at least above 9.5.
SUMMARY OF THE INVENTION
The present invention concerns a drilling process using a foam obtained from a foaming aqueous solution comprising non-ionic surfactants. The foaming solution has a critical temperature referred to as <<cloud point temperature >> or <<cloud point >>.
The cloud point is a characteristic temperature for a solution comprising at least one non-ionic surfactant. The cloud point temperature is known by noting the temperature at which a cloudiness appears in the solution or by knowing the cloud point of the surfactant contained in the solution, the cloud point of the solution being the cloud point of the surfactant. In case of a mixture of two non-ionic surfactants, the cloud point is the average of the cloud points of each of the two components.
It is well-known that, when the temperature of a solution is raised above the cloud point temperature, the homogeneous and isotropic solution divides into two homogeneous and isotropic phases: a phase rich in surfactant and a phase poor in non-ionic surfactant.
The present invention thus concerns a method for circulating a foam in a well, comprising the following stages: whose cloud point temperature and concentration are such that the cloud point temperature of said composition is higher than the temperature of the foam during drilling, to the well bottom, then from the bottom to the surface, temperature at least higher than said cloud point temperature of the composition, so as to destabilize the foam.
In the method, the additive can be a non-ionic surfactant.
The cloud point temperature of the composition can be raised by adding a determined amount of an ionic surfactant.
The cloud point temperature of the composition can be adjusted by adding a determined amount of electrolytes.
The invention also concerns a foaming composition for use in a well drilled in the ground. The composition comprises in combination at least one non-ionic surfactant and an additive consisting of an ionic surfactant, an electrolyte or a mixture thereof, the non-ionic surfactant and said additive having a determined structure and concentration so as to adjust the cloud point temperature of said composition in relation to the temperature of said well.
A viscosifying agent can be added to the composition.
The invention further concerns a system for circulating a foam in a well drilled in the ground, comprising: one additive whose cloud point t
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Argillier Jean-Fran.cedilla.ois
Audibert-Hayet Annie
Zeilinger Sabine
Bagnell David
Dougherty Jennifer R.
Institut Francias Du Petrole
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