SU989043A1 - Buffer fluid - Google Patents

Description

(54) BUFFER LIQUID

The invention relates to the drilling of oil and gas wells, in particular to buffer liquids used to separate the flow of drilling mud and plugging mixture.

It is known to use salt oil or oil as a separator for mud flows and plugging a hydrocarbon-based mixture 1.

However, salt oil and oil do not provide reliable separation of the flow of drilling mud and plugging mixture during their transportation through pipes, which often leads to the premature formation of a non-injected tampon in the pipes and, as a result, to an emergency. This is due to the accelerated process of replacing the salt oil with the drilling fluid, as a result of which the latter comes into contact with the components of the plugging mixture and promotes their hydration, which results in loss of pumpability. This is especially common when pumping a tamponing mixture to depths exceeding 2000 m. Therefore, until recently, a suspension of clay mud or clay cement

mixtures in hydrocarbon liquids, despite their effectiveness, were used at shallow depths.

A buffer fluid is also known for separating the flows of drilling mud and plugging mixture containing aqueous solutions of polyacrylamide and chlorine or sulfuric acid L2J.

This buffer liquid possesses. , visco-elastic properties and reliably separates the flow of drilling and cement slurry water-based. However, when it is used to separate the flow of drilling fluid and the hydrocarbon-based plugging mixture, upon contact with the components of the plugging mixture, the hydrated acceleration of the latter occurs and, as a result, a non-flowing plug is formed at the interface of their contact.

The aim of the invention is to prevent the premature formation of a non-injected tampon in the tubes when using a hydrocarbon-based plugging mixture, h

This goal is achieved by the fact that the buffer fluid for separating the flow of the drilling fluid and plugging mixture containing water, polyacrylamide and salt further contains emult, and sodium chloride is used as a salt in the following ratio of ingredients, wt.%: Polyacrylamide (based on dry matter) 1.4-1.5 12-16.5 Sodium chloride 11-13 Emult Else Water Efficiency The proposed buffer liquids and prototypes are evaluated in laboratory conditions. As a plugging mixture, a suspension of bentonite clay powder in saline oil, which is often used for packing up the absorption zones. The evaluation of the reliability of separation of the flow of the mixture and drilling fluid is done at an experimental installation, which is a V-shaped tube on a rack in which the agent (drilling fluid, flow separator, and plugging mixture) is simulated and the time of pumpability is recorded. Evaluation of the effect on the pumpability of the plugging mixture when mixed with the flow divider in the 2: 1 ratio is performed on a KS-5 consistometer. In this case, the end of pumpability is fixed when the mixture reaches a viscosity of 30 pz. Salt oil is quickly (within 30 seconds) replaced with drilling mud, as a result of which the latter comes into contact with dry mud powder when mixing the boundary layers of the slurry and the drilling fluid after 15 minutes, forms a dense impaction tissue. Prototype when mixed with 5, 0 15.0 20.0 25.0

2 2 2 1 1 1 2 6 form a non-pumpable tampon for 1 min. The results of laboratory studies are shown in the table. Neither Polyacrylamide (experiments 1–3) nor emultal (experiment 16), taken separately and dissolved in water, do not prevent the formation of a non-pumpable tampon in the tubes. Single solutions of two agents in combination. Polyacrylamide-NaC1 (experiments 4–7), polyacrylhydride emult (experiments 8–15) give similar results. The best is. including,%: Polyacrylamide 1-4-1.5, sodium chloride 11-16.5 and emultal 1113, water - the rest. The upper limit of the concentration of the components is established for reasons of economic feasibility, since exceeding it does not give additional advantages to the separator and at the same time worsens the conditions of its preparation. Reducing the lower fringing concentration of polyacrylamide with an optimal composition of the other components leads to the limitation of the pumping time of the suspension through the pipes (experiments 35, 37 and 38). Similar results were obtained by reducing the concentration of NaCl (experiment 39) and emultal (experiments 33 and 34). The proposed composition of the separator of the flow of drilling fluid and components of the plugging mixture in the hydrocarbon medium eliminates the formation of non-pumping tampon in the pipes while eliminating absorption using these mixtures, which makes it possible to expand the area of their effective use without limiting the depth of the absorption zones.

Claims (2)

Continued, tables Note. The invention Buffer liquid containing water, polyacrylamide and salt, is sufficient so that, in order to prevent premature formation of an undamaged tampon in the pipes when using a hydrocarbon-based plugging mixture, it additionally contains emultate and sodium chloride is used as salt the following ratio of ingredients, wt.% s Polyacrylamide (in terms of dry substance) of 1.4-1.5 Continuation of the table Loss of pumpability occurred due to mixing of the plugging mixture with the drilling mud. 12-16.5 Sodium chloride 11-13 Emult Else Sources of information taken into account in the examination 1. Rogers VF Industrial fluids for drilling oil wells,., Gostoptekhizdat, 1960, p. 394, 2. USSR author's certificate No. 732499, class .. E 21 V 33/14, 1977 (prototype),