Research On Automatic Lost Circulation Prevention Technology Of The Functional Compound Gel

In the course of drilling and completion, it is very important to protect the hydrocarbon reservoir for petroligenic natural gas industry. There are a great many factors causing formation damages and their mechanisms vary from each other, so these require formation damage prevention should be settled comprehensively. Lost circulation universally exists while drilling. It may not only bring about severe formation damage, but also impact drilling operation safety. Therefore, this article brings forward new concept and develops new material in terms of mechanism, material, technology etc, so as to settle lost circulation which is a world problem in petroleum-gas industry.By studying the up-to-date technical information of formation damage and lost circulation prevention both domestic and abroad, this article brings forward the new-type multifunction organo-inorganic compound high-strength brainpower gel to temporary plugging and lost circulation prevention technology, and finishes the following critical technology research on organo-inorganic compound high strength brainpower gel:(1) The synthetization and characterization of P(AM-co-AA)a) Select the aqua-solution method of good theory foundation, simple operation, and high-rate polymer production to synthesize copolymer P (AM-co-AA).b) Research the factors impacting copolymer synthetization, many experiments approve monomer ratio, concentration, polymerization temperature and initiator concentration may all take effect on the structure and performance of ultimate copolymer, and through lots of perpendicular experiments, ascertain the optimal experimental program: monomer ratio AM: AA =7:3; monomer concentration: 25%; polymerization temperature: 50℃; initiator concentration: 0.03%. c) Characterization results of the copolymer P (AM-co-AA) prove FT-IR and SEM charts are indicative of great variety with the different contents of copolymer monomer AM and AA.(2) The impacting factor of gelling-course and gel performance of polymer P (AM-co-AA)a) The study of the influence of copolymer concentration to the gel process and gel performance has proven that the marginal gel concentration of copolymer gel system with 30% acroleic acid structural unit content is 0.5%, and the strength of gel and gelling time respectively increases and decreases with copolymer molecular weight increasing.b) If use single aluminum cross linker, the gel strength and gelling time change a little with increasing of concentration of the cross-linking agent. While use compound cross-linking agent, the gelling time increases and gel strength decreases with the citric acid relative ratio of cross-linking agent system increasing.c) With the temperature increasing, the gelling time of polymer gel decreases and the gel strength increases, and the gelling time decreases after increasing for a while with the increasing of pH value. When pH value is 6.5, the gel strength of polymer gel reaches maximum strength.d) The more sodium chloride content in the gel system, the shorter gelling time and the larger gel strength will be, whereas the overall level is low. When [Ca²⁺] is lower than 500ppm, the ultimate strength of gel is free from its impact.(3) The adjustability research of gelling time of blank gel under different temperature conditionsa) The in-door experiment indicates that the gelling time could be adjusted at discretion. We may adjust the gel concentration, the activity, temperature, pH value and content of cross-linking agent to gain the gelling time required.b) Impacts of different temperature increasing course to the polymer gelling time: Although the initial temperature is different, so long as the final temperature is equal, then different temperature increasing course will be little effective on the gelling time of the polymer system.(4) Research on the impact of inorganic material to the gel performancea) Inorganic material granulometric volume (weight) integral distribution curve shows that their particle size distribution is wide, it may be used for plural gel plugging system to plug homologous cracks and pore spaces.b) Adding fibriform, flake, granular inorganic materials into the gel system may increase gel strength and viscosity, but must control the quantity so as to prevent the initial viscosity of organo-inorganic plural gel plugging system increasing quickly, otherwise it may go against pump or field working.c) CaCO₃ particulate material, meerschaum fibrous material can potentiate the polymer P (AM-co-AA) gel, and may enhance gel system strength and shorten the gelling time.d) Gradation experiment indicates that the optimum gradation for gel system is: 400 screen mesh CaCO₃ 0.1%, 800 screen mesh CaCO₃ 0.1%, 1500 screen mesh CaCO₃ 0.3%, meerschaum 0.9%, secondary processed meerschaum 0.9%.(5) Research on the gel rheological property and viscosity-temperature characteristicsa) Through research on shearing stress - shear rate relationship, the yield stress values of four types of plural gel systems are: "+ composite" > "blank gel" (?)("+ fiber" > "+ calcium carbonate", which proves the gel structure of composite have larger strength and tenacity,b) Through research on apparent viscosity - shear rate relationship, the shear-thinning properties of four types of plural gel systems are: "blank gel" > "+ composite" > "+ calcium carbonate" > "+ fiber", which means blanket is easy to infuse and the next is compound material.c) Through research on apparent viscosity - temperature relationship , the durothermic properties of four types of plural gel systems are: "+ fiber" > "+ calcium carbonate" > "blank gel" > "+ composite".(6) Research on lab simulation plugging and field plugging technologya) The lab simulation plugging experiment shows that the glass fiber and inorganic material admixture may reinforce the gel strength of inorganic-organo-plural gel plugging system and viscous force to pipe wall, and it is appropriate to control quantity of the admixture within 1.0-3.0%.b) Environmental temperature has certain effect on polymeric swelling capacity which is not so significant. While environmental temperature is higher than 25.0°C, after swelling of polymer P (AM co AA), the solution viscosity of the polymer approach a constant value. The mineralization ratio has a little effect to the swelling time of polymer, and the higher the concentration of electrolyte solution (mineralization ratio) is, the lower the viscosity of polymer after even swelling will be, and there is no decreasing after increasing while swelling.c) In regard of the field plugging working practice, establish organo—inorganic plural gel plugging field conduct technology.The functional organo-inorganic compound gel studied in the article hereof may have automatic distortion whereas actualize plugging based on pore space, fracture or even the actual cave shape. Furthermore, the gel strength, gelling time may be adjusted as required. This thoroughly changes the plugging methods of simply taking different particle gradation to temporarily plug and plug in drilling and completion operation. On the basis of temporary plugging and plugging mechanisms, it brings forward a kind of fire-new perspective, on the other hand develops a type of new leaking-resistance and lost circulation material, these are of important significance to solve lost circulation or even innovate the formation damage prevention technology.