| The complex block oilfields are widely distributed in China East, mainly in Bohai Bay Basin. Their reserves are hugely big. Of the 58 oilfields, discovered and exploited in Jiyang Depression of Shandong, 39 are complex block oilfields, whose reserves occupy 39.7% of the whole depression. In Dongpu Depression, the complex block reserves take 42.2% of all the reserves. And it is the same in Huanghua Depression. The complex block-Middle 103-1 Block, located in northern Dagang Oilfield, is an anticline structure complicated by faults, walking up to north, with a 14km length and a 4km south-to-north width, and with a structure area about 50km~2. It has complex geological conditions, low permeability, rich faults with small blocks and a big interbedded difference. With oil measurement it can have some producing capacity, but with a fast descent. In order to exploit oil economically, some fracturing reconstruct is needed to increase per-well production.There exists some big difficulties in reconstructing the fracturing of the area of Well 103-1. These difficulties are listed as follows:(l) reservoirs in this area have a low porosity, permeability and layer energy, and also many and thin layers, which can easily cause narrow fracture in fracturing process, thereafter increasing the difficulty in filling sand. The fracturing process of Well Middle 7-59 provides an obvious example for us. This well, with several thin layers, was fractured twice, with the first time only adding the propping agent for 1.7m~3, whose diameter is 0.5～0.8mm and the second time the powder-sand for 8m~3, whose diameter is 1mm, both with general fracturing fluid. These above show that thin layers' fracturing will produce narrow fracture and many bands and the fracturing fluid in the process can easily denudate the band mudstone, thus causing their migration and the pollution to the propping zone. At present in our country, general plant-colloid fracturing fluid is usually applied to fracture this kind of thin oil-layers with a low permeability, which characterizes a large pouring, low beginning, and several-step linear sand addition, whose magnitude is less than 1m~3/m. generally speaking, this kind of operation has a low success and a worse effect than thick layers' fracturing. (2) the fault property is unclear and there is some difficulty in fracturing reconstruct On one hand, in the process of operation, because of the existence of fault, it can produce rich tiny fractures near it, and thus a great loss of fracturing fluid, and thus the high content of mud near it and thus at last a narrow fracturing fracture, which finally causes the difficulty of sand addition. On the other hand, propping agent can easily intrude into the fracture surface after the fracturing, which weakens its connectivity and thus affects the fracturing effect.Aiming at the problems above, we develop a new kind of no-residua fracturing fluid. It is a fracturing fluid system based on viscoelastic surfactant, without any addition of macromolecule polymer. It clears the colloid completely and has no residua. Its denaturalization is completely reversible and it can recover well after shearing. It can also decrease the crude oil's viscosity. The development of no-residua fracturing fluid can well solve the residua problem the plant-colloid...
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