Soluble weighting salt low-damage drilling fluid and preparation method thereof

Abstract

The invention discloses a soluble weighting salt low-damage drilling fluid and a preparation method thereof. The soluble weighting salt low-damage drilling fluid comprises the following components in percentage by mass: 10-20% of organic salt, 3-5% of inorganic salt, 0.1-0.3% of viscosifier, 0.5-1.0% of fluid loss agent, 0.5-5.0% of temporary shielding agent, 0.1-0.3% of alkalinity control agent, 0.03-0.1% of preservative, 0.5-0.8% of deoxidant, 0.1-0.2% of corrosion inhibitor and the balance of water. The soluble weighting salt low-damage drilling fluid disclosed by the invention has stable performance and high liquid phase density, is easy to regulate, realizes good rheological property, can effectively protect the storage layer, maintain stability of the well wall and improve the drilling encounter ratio of the storage layer, and is particularly suitable for a horizontal-section storage layer of mudstone.

Description

technical field [0001] The invention relates to a drilling fluid in oil and gas field drilling operations, in particular to a soluble aggravated salt low-damage drilling fluid suitable for drilling in the horizontal section of a gas storage and a preparation method thereof. Background technique [0002] The construction of gas storage is an important measure for national energy security, mainly to solve the problem of peak shaving of natural gas use. In the prior art, large-scale monolithic deep low-permeability sandstone lithological dry gas reservoirs have large gas fields and thin reservoirs: the thickness of the reservoir is 5-45 meters (average 15 meters), and the permeability is low (average 0.7mD) , low porosity (5%). The buried depth of the gas layer is about 2800m. After long-term exploitation, the pressure of the target layer is extremely low (pressure coefficient 0.4-0.6). Horizontal wells and screen tube completion methods are used to complete the well, which ma...

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Problems solved by technology

However, when this patented technology is applied to the drilling technology of the horizontal well reservoir section, there will be the following problems: 1. The drilling fluid described in this patent is applied to the upper well section. For the collapse of the upper well section, due to the difference in formation, the drilling fluid It cannot solve the problems of wellbore stability and reservoir damage in the horizontal section; 2. The organic potassium salt and weighting agent described in this patent will damage the original reservoir permeability, resulting in a decrease in oil and gas production, so it is not suitable for the horizontal well reservoir section; 3. The drilling fluid described in this patent is solid-phase aggravated, and too much solid phase is easy to invade the formation, causing damage to the reservoir. At the same time, too much solid phase may cause the torque increase in the horizontal section, and the performance of the drilling fluid is not easy to adjust; 4. The patented drilling fluid is mainly used to prevent the collapse of hard and brittle mudstone in the upper well section, but cannot solve the problem of soft mudstone and carbonaceous mudstone collapse in the lower reservoir section

5. As the depth of the horizontal section increases and the temperature of the formation rises, the temperature resistance of the polymer in the drilling fluid mentioned in this patent is low, which cannot meet the higher formation temperature during drilling in the long horizontal section