Due to the presence of starting pressure of low permeability reservoir, so researching on starting pressure gradient of low permeability reservoir is necessary. while starting pressure gradient is relevant to permeability and porosity, it can be obtained through laboratory experiments¡¢well testing interpretation method¡¢theory derivation combined with practical application method . The result of a large number of laboratory experiments shows: starting pressure is related to permeability .The greater the permeability is, the smaller the starting pressure is. They both present the similar hyperbolic relationship; the greater the viscosity of the oil is, the greater the starting pressure is. In this paper, we get the starting pressure gradient formula through the method of theory derivation combined with practical application, meanwhile we put forward the relationship between starting pressure gradient and permeability, porosity¡¢viscosity .

This article analyzes the influence of different branch number, branch length, branch angle on the productivity of the herringbone well. It also summarizes the strongest influence parameters and the weakest influence parameters. Provide theoretical guidance for the formulation of herringbone well development plan. The results show that the maximum effect parameter is branch length, then branch number and branch angle the weakest.

There is an increasing focus on the effective methods to develop low-permeability reservoirs, especially for ultra-low permeability reservoirs. It is hard to achieve the expected stimulation effect only on the traditional single fracturing, because of the poor supply ability from the matrix to fracture in low-permeability reservoirs. Volume stimulating to reservoir, achieving short distance from matrix to fracture because of producing fracture network. So the volume fracturing technology proposed for increasing oil or gas production, this technology is suitable for low porosity and low permeability reservoir. The conventional simulation method can't describe the complex fracture network accurately,but this paper established hydraulic fracturing complex fracture model based on the finite element numerical simulation method , making the simulated complex fracture more close to the real description,it can accurately describe the flow state in the reservoir and cracks.It has an important reference value to the low permeability reservoirs.

Based on the mixed finite element method ，simulated the horizontal well fracturing complex artificial fracture. The article use line elements to describe the horizontal well bore, arbitrary triangle elements to describe the formation. To influence the fracturing horizontal well productivity of artificial fracture parameters are optimized, including the number and fracture length. For different fracture parameters of production dynamic curve carries on the contrast analysis, obtained the different fracture parameters of pressure profile and saturation profile. Research shows that the crack amount and crack length of horizontal well fracturing production dynamic all have obvious influence, but not the bigger the better, there exists optimal value.

Aimed at deflection fracturing by oriented perforation, a two-dimensional, non-steady and two-phase Finite Element Method (FEM) is established. Taking a battery of wells in the inverted nine-spot rhombus pattern as object of study, it is reported that law of different crack initiation angle (CIA) affecting deflection fracturing. In the respect of daily oil production and cumulative oil production, the dual fracture with different CIA is more than straight fracture. So it is feasible to use deflection fracturing of oriented perforation to increase the production of the special low permeability oilfield. In contrast to dual fractures with different fracturing initiation angles, we can see that the wider CIA, the higher cumulative oil production. So we can draw such a conclusion that when deflection fracturing is implemented, angle should be increased if the working condition is permitted so as to increase the production of oil well.