1. Technical Overview
Four Major Technical Issues for Sand-proofing：Powder and Fine Sand Proofing；Gas Well Sand Proof；Sand Proof for Heavy Oil Well；Chemical Sand-fixing Shaft Plug.
Sand control in powder sandstone, argillaceous fine sand rock oil well and gas well development has always being a difficult problem. At present, the most widely used methods are gravel packing (in more than 90% of the sand prevention wells) and fracturing filling sand prevention. In order to ensure the result, it is usually used in conjunction with the sand filter pipe. The blockage problem of the sand filter pipe is common, the flow resistance of the fluid is greatly increased after being blocked, the production capacity of the oil and gas well after sand control is influenced, and the hidden danger is brought to the later workover and sand control operation. In the case of fine sand, the sand filter pipe will be seriously blocked, and the production capacity will decrease rapidly after being put into operation. The problem of gas well is more prominent, due to the blockage of the sand filter pipe, the production capacity is reduced rapidly on the one hand; on the other hand, the other blockage of the other side causes partial concentration of the gas pressure, and the sand-filtering pipe blow-through will cause the sand-proof failure, which is a serious problem that is common and difficult to solve. The problems mentioned above can be solved effectively by shaft block-free chemical sand-fixing technology.
2. Technical background
2.1 Technical Mechanism of Shaft Block-free Sand-fixing Technology
Shaft block-free sand-fixing technology has the physicochemical effect of converting chemical energy into mechanical energy, the effective component can firmly consolidate the formation of sand (quartz sand) under certain filtration conditions, and the solidified body has sufficient phase permeability. The technology has incomparable excellent performance and characteristics when compared with previous sand-fixing agents and the sand-stabilizing agents.
Shaft block-free sand-fixing agents is composed of type A and B high polymer materials, which can contract with the formation of sand after the consolidation action at a certain temperature so as to ensure firm combination of the formation of sand (quartz sand). The permeability of the oil layer can be effectively maintained under the condition of effectively preventing the formation of the stratum; At the same time, the migration of formation sand and its particles in the production layer is fundamentally controlled, which establishes an effective sand-retaining barrier.
2.2 Technical Characteristics
2.2.1 Most effective in powder and fine sand prevention for high mud concentrated and loose sandstone reservoirs
2.2.2Small influence on permeability and oil gas well productivity
2.2.3Strong adaptability to gas wells with higher gas production strength
2.2.4No blockage in well, so as to meet the requirements of various special shaft conditions
2.2.5Also applicable to casing deformation well
2.2.6 Low sand-proofing cost
3.Application Scope and Principle of Oil Well Selection
3.1 Technical Adaptability
3.1.1 The fine sand can be consolidated well, and also highly adaptable for formation in high clay content (for example, greater than 40%).
3.1.2 Applicable to sand-proofing in special wellbore conditions.
3.1.3 Well sealing time for coagulation: 48h (below 60 ℃), 24h (above 60 ℃).
3.2 Principles of Well Selection
3.2.1 Oil-water wells with good quality of well concentration;
3.2.2 Shakeout well with relatively small interlayer difference and oil well with relatively high water content;
3.2.3 High clay content and high fine sand content;
3.2.4 Well with low viscosity of crude oil and smaller flow drag force;
3.2.5Oil well with short anti-sand shelf life;
3.2.6The wellbore interval should not be too long;
3.2.7It is suitable for the application of various types of wells, i.e. requirements of special operation wells (such as casing deformation well, small diameter casing, sidetracking well, highly-deviated well, horizontal well, etc.).
4. Technical Indicators
5. Performance Evaluation
6. Effectiveness Evaluation of On-site Test
Shaft block-free sand-fixing technology for high mud content loosen powder/fine sand in sandstone oil/gas well has been successfully adopted in straight well, horizontal well and side drilling well.
6.1 G4-13-CP12 well
G4-13-CP12 well, production layer 44: 1388.7-1432.35m (lost seal 1474.85-1508.85m), was put into operation in October 2008, liquid volume 3/ 2.1/ 30%, on the 84th day of production, due to low liquid volume, was suspended for repair probing, and no sand was detected. 2.2/ 2.0/ 7.0% after completion of the well, and low liquid volume still existed. After 117 days of production, BJ company was contacted for continuous oil pipe mud cake for blockage, 2.4/ 2.0/ 5.2% after completion of the well, and the effect is not obvious. After 61 days of production, the new type well bore hole without plugging material was used to prevent sand proofing. Construction data: 10% cleaning agent of 6m3 was applied, replacing 6m3 of clear water, with 10.0MPa pump pressure and 300L/ min of displacement. Forward extrusion of new HY sand proofing material of 8.0m3 is applied, the pressure is 10.0MPa, and the displacement is 300L/ min. Replace clean water 4.0m3, pump pressure 10.0MPa, displacement 300L/ min. After 24h of the waiting period, no sand was detected .Completion production 23.3/12/48%. Ongoing production 30/ 9.2 /69.3%.Additional oil production as of the end of 2009 was more than 1100 tons.
6.2 KD642-P1 well
KD642-P1 well, production layer: 55: 1473.6-151.73 m, put into operation in March 2008, the amount of liquid in the production volume is 19.0/ 9600/ 10.2%, and after 372 days of production gas injection, the production lasted for 77 days before sand blockage. The sand detection surface is 1385. 18m, 1.2m3 of formation sand is punched out, 17.5/10 /42.5% upon well completion. Sand proofing is done after 105 days of production, sand is detected after 105 days of production, the sand layer is at 1457. 61m, formation sand extracted was 1. 5m3, and the contact measure adopts a new type of shaft without the material for sand prevention. Construction data: applied 10% of the cleaning agent at 6m3, positive water replacement is 5m3, the pump pressure is 1.0MPa, and the displacement is 300L/ min. The new HY sand proofing material is being squeezed for 10. 0m3, and the displacement is 300L/ min .Clean water replacement was 6.0m3, pump pressure 1.0MPa, displacement 300L/ min. After setting up for 12h, no sand was detected, 12/ 6.2/ 4.7% of the production upon well completion. 50 days of normal production as of the end of 2009, and 270 tons of oil was accumulated.
7.Conclusion
7.1 Compared with conventional chemical sand control materials, the blockage-free material is featured with high sand control ability (high consolidation strength) and lower oil layer damage rate (high permeability retention ratio after consolidation) than the conventional chemical sand control material.
7.2 Another feature of material is that the quartz surface has a strong binding effect under the condition of filter loss, and no slug is formed in the water, and the purpose of leaving the plug in the wellbore after construction is realized.
7.3 HY sand fixing technology does not need sand proofing crew, simple and convenient in construction and operation, with wide application prospect in special wells (casing deformation well, small diameter casing, side drilling, large slope well, horizontal well etc.) as well as high mud content and loose fine sand rock reservoirs.
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