CN103256034A - Two important methods for improving steam stimulation effect - Google Patents

Abstract

Steam stimulation is a core technology in reservoir thermal recovery methods; however, with the in-depth development of stimulation stages, a plurality of defects such as quick degression in periodical oil production, short period of stable production and greatly rising economic cost are revealed in production. By deep research on fluid migration rules during stimulation, existing defects in steam injection parameter design and limitation of composite steam stimulation, two important methods for improving steam stimulation effect are proposed purposefully. The methods are simple and effective, economic cost is prevented from rising greatly, but considerable economic benefit can be brought to steam stimulation thermal recovery development, and influence is far-reaching.

Description

Improve two important method of steam soak effect

Technical field

This method is applicable to all kinds of oil reservoirs of thermal process exploitation of handling up of applying steam in the oil exploitation industry.Be primarily aimed at problems such as steam soak heat effect is low, the Simulation on whole pay zones duration short, the stable yields time is short, lapse rate is high, the life cycle of handling up is short, gas oil ratio reaches economic technology parameter 0.15 very soon and propose the improvement method.

Background technology

Steam soak is one of effective development tool of Simulation on whole pay zones oil reservoir, but along with the deepening continuously of exploitation, exposes increasing problem in the production, such as, 1) 2 ~ 3 cycles annotate not advance, yield poorly; 2) thin-medium bed oil reservoir cycle of handling up lacks, and high round is handled up, and is high moisture, yields poorly; 3) the oil production decline rate is fast in the monocycle, and end cycle early; 4) the oil well complete period oil production of handling up also presents this Changing Pattern, and peak of curve is milder.On oil production method, many wells integral body is handled up, handle up intermittence, notes are adopted equal energy more and improved high wheel well steam soak effect, reduce production costs, but on alleviating aspect the old well decline rate, can only work to a certain extent, but can't solve the handle up general trend of deleterious of high wheel well.Technology such as many wells integral body is handled up, handle up intermittence, notes are adopted more all have certain applicable elements and limitation.The whole steam soak effect of many wells can only connect the 2-3 wheel, continues the deleterious of handling up; Intermittently handling up is a kind of way of changing the space with the time, is applicable to poor efficiency well and long-term dead well; More one notes are adopted and are more suitable in dense well spacing, huge chunk shape oil reservoir.The cycle change of production rule of handling up is as Fig. 1, Fig. 2.

Summary of the invention

Inventive principle:

1) under the saturated methane gas condition, along with temperature and pressure increase, the viscosity of in-place oil reduces, and annotates under the vapour condition, and in-place oil will experience once by plasticity half curdled appearance to viscous fluid again to the sloppy condition transition process, and temperature reduces, inverse process.That is to say, want extraction crude oil effectively, annotate the necessary first preheating stratum of stripping heat supply energy, set up necessary thermal field, make crude oil enter flow regime, simultaneously, also will have follow-up enough heat energy to guarantee that flowable crude stream is to the shaft bottom.Therefore, along with the round of handling up increases, the thermal recovery radius increases, and the vapour cavity volume increases, and vapour chamber surface area increases, and required heat energy is more many, and the crude stream that is heated is more high to shaft bottom institute energy requirement;

2) crude oil flow state: influenced by the every factor of Simulation on whole pay zones and crude oil self physical property, by between well to the near wellbore zone, super viscosity of thickened oil reduces gradually, mobility strengthens, excessive to flow regime by plasticity half curdled appearance, in the thermal process, crude oil is successively peeled off, similar ice sheet melts, and this properties influence is handled up or vapour drives the mode rate of oil production;

3) form theory according to Marx-langenheim thermal recovery principle and vapor chamber, the Simulation on whole pay zones middle and later periods, super viscous crude remaining oil mainly is distributed in hot bypassed area between well, and the aspect image-tape has the sandy beach of ripple mark.But be subjected to gravity and inject the influence that steam replenishes heat energy, the trend that the direction that the oriented fluid potential energy of remaining oil viscous fluid is low flows, therefore, under the acting in conjunction of multiple factor, the super viscous crude remaining oil distribution of development late stage mainly concentrates on the oil reservoir bottom and is the running surface form and exists.By reservoir pore space capillary tube attraction function and gravitational differentiation influence, the in-place oil oil saturation presents from top to bottom, be to oil saturation between well by producing well and increase progressively state, and heating power bypassed area saturation ratio is initial oil saturation;

4) in actual development and Design, steam injection parameter is generally individual event relatively, as annotate vapour amount and gas oil ratio relation, annotate the relation of vapour intensity and gas oil ratio etc., just the gained steam injection parameter remains unchanged after entering the produce oil peak period, as: a. notes vapour mass dryness fraction: the shaft bottom steam quality guarantees greater than 40%; B. the period 1 is annotated vapour intensity: alternating layers shape oil reservoir 80t/m, massive oil pool 70t/m; C. the cycle is annotated vapour strength increase amplitude: second, third cycle annotates vapour intensity and increases progressively 10% ~ 15% in last cycle basis, the four ~ six cycle annotated the vapour more last cycle of intensity and increases progressively 5% ~ 10%, annotated vapour intensity remain unchanged (horizontal well is constant after the period 5) after the period 6; D. steam injection rate: the initial stage alternating layers shape oil reservoir steam injection rate 200t/d that handles up, thick-layer massive oil pool steam injection rate 180t/d; The intermediary and later stages alternating layers shape oil reservoir steam injection rate 240～320t/d that handles up, thick-layer massive oil pool steam injection rate 220～300t/d; E. boil in a covered pot over a slow fire the well time: 3 ~ 5 days.This does not obviously conform to migration rule and institute's energy requirement of oil gas in the Simulation on whole pay zones process, and therefore, throughput efficiency is low, and production decline is fast, and final recovery percent of reserves is influenced.

According to above-mentioned principle analysis, special according to two kinds of cyclic steam stimulation methods of different situations design, the core concept of method, the one, adjusting steam injection parameter has enough heat energy to flow to the shaft bottom to guarantee the mobile crude oil of preheating; The 2nd, slow down the stratum heat-energy losses, improve the cycle oil production, slow down cycle oil production lapse rate, prolong steam soak stable production period.Concrete grammar is as follows:

Method one: at six all after date production decline situations, should adjust steam injection parameter according to heating radius, it is as follows that steam injection parameter is adjusted formula of reduction in good time:

Q _（dvtp）=CμQ _OrV

Q _(dvtp): cyclic steam injection volume, mass dryness fraction, speed, temperature and pressure function;

C: production-injection ratio;

Q _O: the cycle oil production;

R: oil recovery radius;

V: the vapour cavity volume, available oil production converts

According to each oil reservoir feature, select combined type to annotate way of steam and the on-the-spot steam injection parameter of dynamic adjustment, will obtain considerable economic well-being of workers and staff.The Marx-langenheim formula is commonly used to design the final thermal recovery radius of oil reservoir steam soak, i.e. well spacing design, but by thinking, this formula can be used as the reference of the on-the-spot steam injection parameter of dynamic adjustment:

$\mathrm{Ar}=\frac{I_s{h}_{m}h{M}_R{\mathrm{\α}}_s}{4{\mathrm{\λ}}_s^2(T_s-T_i)}(e^{t_D}\·\mathrm{erfc}\sqrt{t_D}+2\sqrt{\frac{t_D}{\mathrm{\π}}}-1)$

$r_h=\sqrt{A_r/E_A.\mathrm{\π}}$

d?=?2.r _h

Is---?injection?rate，kg/h；

h?---?net?pay?thickness，m；

hm?---?the?enthalpy?of?saturated?vapor，kcal/kg；

λ _S?---?thermal?conductivity?factor?of?top?and?bottom?layer，

kcal/（h.m.℃）

M _R?---?thermal?capacity?of?the?oil?layer，kcal/kg；

α _S?---?the?thermal?diffusivity?of?top?and?bottom?layer，m ²/h；

Ts，Ti?---?the?temperature?of?steam?and?original?oil?layer，℃；

T?---?time?of?injection，h；

Ar?---?the?area?of?heated?zone，m ²；

T _D?---?dimentionless?time；

erfc---?error?penalty?coefficient

r _h?---?heated?radium，m；

d?---?reasonable?well?spacing，m；

EA---?heat?capacity，m；

Method two: replace the steam soak well pattern, as Fig. 3, Fig. 4, Fig. 5.This alternately steam soak well pattern method of handling up is, black walling crib well pattern is annotated the vexed well of vapour earlier, and when beginning to produce, light grey walling crib well pattern is annotated the vexed well of vapour again, the heat that injects remedies the former the middle and later periods heat-energy losses of handling up, and guarantees that having more thermal energy to keep fluid flow to the shaft bottom; When the black well pattern enters a new round when annotating vapour, the loss that the new heat energy that injects comes to replenish light grey well pattern heat energy again, both rotate steam soak, as Fig. 6, hand over mutually and echo, and reach and keep stratum energy, the handle up purpose of thermal recovery effect of raising

Description of drawings

Fig. 1 is the change of production rule figure that handles up in the different layers position straight well cycle, and abscissa is periodicity, and ordinate is tired oil production (t) of cycle, three tired oil production of cycle that curve is represented three different layers positions;

Fig. 2 is straight well individual well production per cycle graph of relation, and transverse axis is time (d), and the longitudinal axis is daily output (t/d), day moisture content (%), and the first row curve is moisture content (%), and the second row curve is the daily fluid production rate curve, and the third line curve is the daily oil production curve;

Fig. 3 is triangle seven spot pattern figure, and grid line is the form of well pattern, and the black walling crib is the well pattern of handling up, and light grey walling crib is another well pattern of handling up;

Fig. 4 is square five-spot pattern figure, and grid line is the form of well pattern, and the black walling crib is the well pattern of handling up, and light grey walling crib is another well pattern of handling up;

Fig. 5 is square nine-spot pattern figure, and grid line is the form of well pattern, and the black walling crib is the well pattern of handling up, and light grey walling crib is another well pattern of handling up;

Fig. 6 replaces steam soak well pattern production cycle output matching relationship figure, and this figure is two and replaces different two mouthfuls of straight well production per cycles corresponding relation in time in the well pattern, is a schematic diagram, and horizontal ordinate is consistent with the represented content of curve and Fig. 2 among the figure.

Claims (1)

1. improve two important method of steam soak effect, the characteristics of method one are, after steam soak enters the middle and later periods, steam injection parameter needs along with adjustment is further strengthened in the expansion of heating radius and the increase of vapour cavity volume, to guarantee that the preheating fluid flow to the shaft bottom, prolong the whole life cycle of handling up, formula of reduction is:

Q _(dvtp)=CμQ _orV

Q _(dvtp): cyclic steam injection volume, notes vapour mass dryness fraction, steam injection rate, steam injecting temperature and steam injection pressure function

C: production-injection ratio

μ: in-place oil viscosity

Q _o: the cycle oil production

R: oil recovery radius

V: the vapour cavity volume, convert with oil production

The characteristics of method two are, the steam soak well pattern is split into two covers (or three covers) well pattern, and steam soak then hockets, stable to keep stratum heat energy, guarantee that the preheating fluid fully flow to the shaft bottom, slows down cycle oil production lapse rate, stable production period in prolongation cycle, improve oil recovery factor.

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