1.1.3 environmentally friendly fluid loss additive

With the increasing attention to environmental protection, foreign researchers have increased the research and development of environmentally friendly fluid loss additive in recent years. The so-called environmentally friendly fluid loss additive refers to the product with good biodegradability. At present, the main ways to develop environmentally friendly fluid loss additive are:  

1) to develop natural products with filtration function;  

2) to modify the existing natural product fluid loss additive and broaden its application scope;  

3) to develop fluid loss additive which is stable in strong alkaline environment and degraded in neutral water medium 

4) Low molecular weight polymer was crosslinked with degradable crosslinking agent to obtain high molecular weight fluid loss additive 

5) The degradable synthetic polymer was modified to reduce filtration 

6) A synthetic polymer fluid loss additive with similar structure to natural products and degradable by microorganisms was developed.

1.2 research progress of Retarder

There are many kinds of retarders, including lignosulfonate and its derivatives, low molecular weight cellulose and its derivatives, hydroxy carboxylic acid (salt), organic phosphonic acid (salt), boric acid (salt), complex, etc. In recent years, continuous improvement has been made for the defects of the original retarder at home and abroad, and some new retarders have been developed. From the point of view of molecular weight or synthesis method, it can be divided into two categories: organic compounds and polymers. Most of the organic compounds studied are organic phosphonates. The polymer used as retarder is usually oligomer with molecular weight of several thousand, which is mostly prepared by copolymerization. The polymer with carboxyl group, phosphonic acid group and sulfonic acid group is the most studied one. Relatively speaking, organic retarders such as hydroxy carboxylic acid (salt) and organic phosphonic acid (salt) are less, but more sensitive; However, the dosage of polymer retarder is large, but the linear relationship between dosage and thickening time is good.

1.2.1 organic retarder

There are many kinds of organic phosphonic acids (salts), many of which are suitable for oil well cement retarder.

Foreign patent reports. Example 1: methylenephosphonic acid derivative is used as superfine cement retarder, and the service temperature can reach above 116 ℃. Example 2: methylenephosphonic acid derivative and borax are used as high temperature retarder according to the mass ratio of (0025-02): 1, and the methylenephosphonic acid derivative is selected from calcium ethylenediamine tetramethylidene phosphonate, sodium ethylenediamine tetramethylidene phosphonate and ethylenediamine pentamethylidene phosphonate. The retarder is suitable for 121-260 ℃ (BHST), and it is suitable for cementing in high temperature deep wells with long cementing section. Example 3: organic phosphonic acid (salt) and inorganic phosphoric acid (salt) are used as retarder in a certain proportion. In addition, retarder can be added to expand the application temperature range. The composition of a recommended retarder is as follows: 10-15% EDTMP sodium calcium, 40-45% phosphoric acid and 40-50% retarder enhancer. The effective temperature of the http://www.zoranoc.comretarder is 70-140 ℃.

Domestic research results. Example 1: hydroxydiamine methylidene phosphonic acid was synthesized and used as high temperature retarder in the temperature range of 50-170 ℃. Example 2: an unsaturated amine compound is used to react with phosphite and formaldehyde to form alkylene phosphonate as retarder. The temperature range is 40-170 ℃, and the comprehensive performance is better than that of the synthetic product of dimethylamine, phosphite and formaldehyde.