Structural failure mechanism and strengthening method of fracture plugging zone for lost circulation control in deep naturally fractured reservoirs

XU Chengyuan,YAN Xiaopeng,KANG Yili,YOU Lijun,ZHANG Jingyi

Table 4 Experimental sample formulation and results of fracture plugging evaluation.

Num- ber	Formula	Fracture module	Maximum plugging pressure/MPa	Total loss volume/ mL
Base drilling fluids	0# diesel oil (42%-48%) + Main emulsifier (2%-3%) + Auxiliary emulsifier (2%-3%) + Calcium chloride aqueous solution (3.0%-4.5%) + Lime (2.0%-4.5%) + Fluid loss additive (2.0%-2.5%) + Tackifier (0.5%-0.8%) + Suspending agent (0.3%-0.6%) + Fluid flow pattern regulator (0.2%-0.5%) + Wetting agent (0.2%-0.5%) + Anti sloughing agent (1.2%-2.0%) + Weighting agent	Fracture width 0.15 mm	2.2	>100
1-0#	3% Bridging material K3 + 3% Bridging material K4 + 3% Bridging material K5 + 3% Bridging material G12 + 3% Filling material G7 + 4% Filling material G10 + 3% Filling material D21 + 0.8% Fiber G8	Fracture width with inlet 8 mm and outlet 5 mm	7.9	250
1-1#	5% Bridging material K3 + 3% Bridging material K4 + 3% Bridging material K5 + 3% Bridging material G12 + 3% Filling material G7 + 4% Filling materials G10 + 3% Filling material D21 + 0.8% Fibre G8	Fracture width with inlet 8 mm and outlet 5 mm	>20.0	77
2-0#	3% Bridging material D11 + 3% Filling material G14 + 0.2% Fiber G8	Fracture width with inlet 3 mm and outlet 1 mm	9.4	19
2-1#	3% Bridging material D11 + 3% Filling material G14 + 0.2% Fiber G9	Fracture width with inlet 3 mm and outlet 1 mm	11.2	9
3-0#	7% Bridging material G7 + 2% Bridging material K3 + 4% Bridging material G4 + 5% Bridging material G6 + 3% Bridging material K4 + 5% Filling material K5 + 10% Filling material G10 + 0.8% Fiber G9	Fracture width with inlet 8 mm and outlet 5 mm	5.0	130
3-1#	4% Bridging material G7 + 5% Bridging material K3 + 4% Bridging material G4 + 5% Bridging material G6 + 3% Bridging material K4 + 5% Filling material K5 + 10% Filling material G10 + 0.8% Fiber G9	Fracture width with inlet 8 mm and outlet 5 mm	>20.0	20
4-0#	6% Bridging material K4 + 5% Bridging material K3 + 3% Bridging material K5 + 3% Filling material G15 + 4% Filling material K6 + 3% filling materials D21 + 0.8% Fiber G8	Fracture width with inlet 8 mm and outlet 5 mm	18.0	20
4-1#	3% Bridging material K4 + 3% Bridging material D2 + 5% Bridging material K3 + 3% Bridging material K5 + 3% Filling material G15 + 4% Filling material K6 + 3% Filling material D21 + 0.8% Fiber G8	Fracture width with inlet 8 mm and outlet 5 mm	>20.0	40