Precautions and Preventive Measures of Hydroxyethyl Cellulose in OilDrilling
HydroxyEthyl Cellulose (HEC) has a remarkable feature, that is, when it is added to the slightly acidic water, it has the effect of delaying producing the viscosity. The period of time needed from the start to thickening helps HydroxyEthyl Cellulose particles to be uniformly and thoroughly dispersed without agglomeration so as to obtain the gel solution. The PH value of solution can be increased to 9-10, and thickening effects can be produced within 15 minutes. And heating the solution or raising the temperature helps to promote dissolution of the Hydroxyethyl Cellulose.
In the oilwell work site, HydroxyEthyl Cellulose solution is prepared in batches by the mixing tank under neutral to slightly acidic PH conditions, and keep HydroxyEthyl Cellulose in a good state of dispersion. As for the field use, just add caustic soda and the viscosity can be immediately generated. In operation with the slurry gun, it should be noted that the nozzle should be n inserted into the liquid, and the purpose of doing so is to avoid producing foam.
2. Anti-Enzyme Problem
Since Hydroxy Ethyl Cellulose is obtained from cellulose, inevitably, it is susceptible to hydrolysis and may lose viscosity. This nature is conducive to the compound use of Hydroxyethyl Cellulose with the demulsifier in the completion and workover process. But in the preparation of drilling fluids, it must be noted that biocides should be used for treatment in order to avoid the production of bacterial enzyme varieties. Once the dispersion of bacteria has occurred, then even if remedial measures are taken again to kill the bacteria, in a period of time the enzyme formed by the bacterial dispersion would still make HydroxyEthyl Cellulose degraded, which may still cause the loss of viscosity, so be sure to take preventive measures. Attention should be paid to another point— absolutely do not use surface overflow water for the preparation of drilling fluid, because water of this type is likely to contain the enzyme and in a very short period of time can completely destroy the Hydroxyethyl Cellulose solution.
3. Anti-forming Agents
In the process of drilling, etc., the working fluid is easy to produce bubbles, which must be removed or avoided as much as possible. Polypropylene substances, SAG siloxane, etc. may well be effective anti-forming agents for HydroxyEthyl Cellulose solution, but its usage must be experimented depending on the site conditions.
In short, in the oil field, for the use of Hydroxyethyl Cellulose, pay attention to five main points:
(1). During adding materials. And keep stirring. All viscosity generated in the cycle before stirring. Continuously stir in cycles before the generation of the total viscosity.
(2). The nature of water can affect the dissolution time. When either the pH value or the temperature is increased, then the time of complete hydration will be shortened. Before HydroxyEthyl Cellulose has not been completely dispersed, do not rush to increase the pH vale of water.
(3). Slowly add the material through the mud funnel (100kg HydroxyEthyl Cellulose/15 minutes).
(4). Add effective preservatives and fungicide to prevent the occurrence of enzymatic hydrolysis.
(5). In order to prevent HydroxyEthyl Cellulose from absorbing moisture, the HydroxyEthyl Cellulose that has been unpacked but has not yet run out for once, shall be airtight stored.
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