CN105257288A - Method for determining tight reservoir original reservoir pressure based on injection pressure decline well testing technology - Google Patents

Abstract

The invention provides a method for determining tight reservoir original reservoir pressure based on the injection pressure decline well testing technology. The method comprises the steps that liquid is injected into a reservoir according to the designed displacement before pressure cracking modification; downhole shut-in is performed, and shaft bottom data are recorded; the data are processed to obtain tight reservoir original reservoir pressure. The tight reservoir original reservoir pressure is determined in a downhole shut-in pressure measuring mode, the traditional well testing technology connotation is expanded, and tight reservoir original pressure features can be better reflected, and the better scientific bases are provided for knowing reservoir features, predicating single-well real capacity and guiding reasonable production allocation.

Description

Based on the method for injection pressure drop Well Test Technology determination compact reservoir original formation pressure

Technical field

The present invention relates to exploration of oil and gas field field, be specifically related to a kind of method based on injection pressure drop Well testing determination compact reservoir original formation pressure.

Background technology

Poor by reservoir permeability, yield poorly, the impact of the factor such as recovery time is long, conventional well-logging method is difficult to determine compact reservoir original formation pressure.Domestic large scale investment exploitation shale, Sandstone Gas Reservoir in recent years, the data that the strata pressure of its compact reservoir mainly obtains by carrying out wellhead shut-in after massive hydraulic fracture at present calculate.The strata pressure of compact reservoir can not represent reset pressure characteristic, and existing initial production capacity all adopts this pressure to predict, cannot reflect the true production capacity of reservoir.

Although industry is generally used by the method for injection pressure drop Well testing determination bed gas reservoir original formation pressure, test technology and analytical method are all ripe, and adopt wellhead shut-in pressure measurement mode, data quality is not high.

Summary of the invention

The object of the invention is to the deficiency overcoming the existence of above-mentioned technology, provide a kind of method based on injection pressure drop Well testing determination compact reservoir original formation pressure, the method comprises:

(1) liquid is injected to compact reservoir;

(2) downhole closing is carried out, admission shaft bottom data;

(3) injection and closing well data information are processed, obtain compact reservoir original formation pressure.

Do not carry out fracturing reform before the described compact reservoir of step (1) injects liquid, described liquid is smooth liquid.

Step (1) described injection is fluid operated to be carried out continuously with the described closing well operation of step (2).

The described data process of step (3) is mainly G-function drawdown analysis method, the straight line being specially initial point offsets downward along G-function differential of pressure curve, and original formation pressure is determined in the position overlapped with G-function differential of pressure curve, G-function pressure semilog derivative curve intersection point.

The present invention adopts injection pressure drop Well testing, by downhole closing pressure measurement mode determination compact reservoir original formation pressure, expand the intension of traditional Well Test Technology, compact reservoir reset pressure characteristic can be reflected preferably, for understanding reservoir characteristic, the prediction true production capacity of individual well and instructing rational proration to provide good scientific basis.

Accompanying drawing explanation

Fig. 1 is injection pressure drop Well testing ground of the present invention injection device operating diagram;

Fig. 2 is injection pressure drop Well testing downhole closing equipment schematic diagram of the present invention;

Fig. 3 is shale gas X well on-the-spot test pressure temperature curve of the present invention;

Fig. 4 is data process G-function drawdown analysis curve of the present invention.

Detailed description of the invention

Describe the present invention below in conjunction with drawings and the specific embodiments.

Injection pressure drop well testing test ground injection device of the present invention and downhole closing equipment schematic diagram are respectively as depicted in figs. 1 and 2, above ground portion comprises water tank, injection pump, high pressure pipe joint, flow meter, pressure meter etc., and underground part comprises packer, underground switching valve, down-hole pressure recorder etc.

The principle of determination compact reservoir original formation pressure of the present invention is as follows:

$p_{ws}=p_i+\frac{2.12\×{10}^{-3}qB\mathrm{\μ}}{kh}\lg \left(\frac{t_p+\mathrm{\Δ}t}{\mathrm{\Δ}t}\right)---\left(1\right)$

In formula, q is that fluid injects discharge capacity, m ³/ d;

P _wsfor bottom hole flowing pressure, MPa;

P _ifor original formation pressure, MPa;

μ is for injecting fluid viscosity, mPas;

B is fluid volume coefficient, dimensionless;

K is reservoir permeability, mD;

H is reservoir thickness, m;

T _pfor injection length, h;

△ t is the closed-in time, h.

Wherein, p _wewith relation be straight line, its slope is

The present invention has carried out on-the-spot test for certain block shale gas well domestic.On September 5th, 2013,22:30-22:40 was to shale gas X well Lower Silurian Series Longma small stream group--upper Ordovician series five peak group, well section 2815.00-2818.00m (thickness 3m) cable transmission perforation.September 6,1:00-3:31 carried out squeezing test, operation pressure 23.4-26.8MPa, fracture pressure 24.3MPa, operational discharge capacity 1.04m ³/ min, termination of pumping pressure 18.7MPa, clamp-ons slippery water 7.2m ³, be down to 12.6MPa to 8:20 monitoring pressure on September 10 by 18.7MPa.Test period, injection process and closing well process are carried out continuously, and continuous monitor well bottom pressure.

The X well on-the-spot test pressure temperature curve that monitoring obtains as shown in Figure 3.

By carrying out G-function differentiate to underground monitoring flowing pressure, G-function semilog differentiate process obtains Fig. 4.Offset downward along G-function differential of pressure curve according to from initial point straight line out, the position overlapped with G-function differential of pressure curve, both G-function pressure semilog derivative curves intersection point to determine bottom pressure during closing up of cracks, thus obtains original formation pressure.

According to construction parameter: formation fracture pressure 24.3MPa, inject discharge capacity 1.04m ³/ min, fluid viscosity μ=0.95mPas, fluid volume coefficient B=1m ³/ m ³, injection length t _p=2.52h, closed-in time △ t=100.82h, formation porosity K=0.05, wellbore radius r _w=0.057m, compression coefficient Ct=0.00435, reservoir thickness h=3.0m, obtaining compact reservoir original formation pressure by G-function drawdown analysis is 18.35MPa.

Claims (4)

1., based on the method for injection pressure drop Well testing determination compact reservoir original formation pressure, it is characterized in that comprising the following steps:

(1) liquid is injected to compact reservoir;

(2) downhole closing is carried out, admission shaft bottom data;

(3) injection and closing well data information are processed, obtain compact reservoir original formation pressure.

2. the method determining compact reservoir original formation pressure according to claim 1, is characterized in that: do not carry out fracturing reform before the described compact reservoir of step (1) injects liquid, described liquid is smooth liquid.

3. the method determining compact reservoir original formation pressure according to claim 1, is characterized in that: step (1) described injection is fluid operated to be carried out continuously with the described closing well operation of step (2).

4. the method determining compact reservoir original formation pressure according to claim 1, it is characterized in that: the data process described in step (3) comprises G-function drawdown analysis method, the straight line being specially initial point offsets downward along G-function differential of pressure curve, and original formation pressure is determined in the position overlapped with G-function differential of pressure curve, G-function pressure semilog derivative curve intersection point.