CN1052524C

CN1052524C - Mineralizing gradient water-filling method for low-permeable reservoir

Info

Publication number: CN1052524C
Application number: CN96119421A
Authority: CN
Inventors: 宫立武; 刘安健
Original assignee: Drilling-Extracting Process Inst Liaohe Petroleum Exploration Administration (
Current assignee: Drilling-Extracting Process Inst Liaohe Petroleum Exploration Administration (
Priority date: 1996-09-16
Filing date: 1996-09-16
Publication date: 2000-05-17
Anticipated expiration: 2016-09-16
Also published as: CN1148660A

Abstract

The present invention relates to a low-permeability reservoir mineralization degree water injection method which is based on an activity equilibrium theory. Firstly, injection water with the mineralization degree of stratum water is injected into strata; then, the mineralization degree of the injection water is gradually decreased; finally, normal freshwater is injected after water injection for a plurality of periods. Therefore, the relative equilibrium of the mineralization degree of the injection water and the stratum water can be kept, and the damage to the permeability of reservoirs caused by the hydrating expansion of clay can be greatly reduced. Since the water injection method is capable of keeping the long-term and stable water injection of oilfields and has the characteristics of low cost, convenient construction, etc., the water injection method can be popularized and used in converted production wells newly invested in the oilfields.

Description

Mineralizing gradient water-filling method for low-permeable reservoir

The invention belongs to the method for oil field underground water-injection operation raising water injection rate, particularly relate to a kind of salinity gradient water-filling method that improves low-permeability reservoirs that is applicable to.

The oil field is for high yield steady in a long-term, need remain on the mining type under the original formation pressure state, and adopt to the stratum water filling is to improve a kind of effective measures of oil recovery factor also to be used widely, this has meaning of crucial importance for improving oil recovery factor how to keep stablizing water filling, in the conventional waterflooding operation, inject the injury of water in order to reduce to the reservoir, not only need injecting outside water quality handles, also will add sticking scholar's stabilizing agent and cause the in-place permeability infringement and bring the low consequence of water injection rate, but this method is difficult to realize to prevent the reservoir hydration and expansion of clay to the serious stratum of down-hole water sensitivity; 1986-1995 " american petroleum digest " and " external oil gas science and technology " low permeability reservoir are developed new direction and new technology " Oil-Gas Field Development Engineering collected translation " by retrieval in addition, all be engaged in number of research projects aspect the exploitation of low-permeability oil deposit both at home and abroad as can be seen from the situation of retrieval, many concrete grammars have also been proposed, have for the measure of abroad taking under low permeability reservoir and the argillic horizon content condition with higher: hot-water flooding, the circulation water filling, CO ₂-foam flooding or the like, and overseas utilization salinity gradient injection technique is used in the exploitation of polymer injection more.These all are the very strong measures of specific aim, and wherein hot-water flooding and circulation water filling steam have also all been obtained better effects, and adopt straight the present of method of the present invention not to be reported.

Task of the present invention is that propose for the shortcoming that overcomes said method a kind of can be in the salinity gradient water-filling technology of low infiltration sandrock reservoir.So as to improving the injection rate of injecting well.

Implementation of the present invention is:

The present invention is mainly to be to be caused by osmosis according to underground reservoir hydration and expansion of clay principle, in water injection well in oil fields, be lower than under the salinity situation of stratum mud shale moisture content especially owing to injecting water salinity, cause hydration and expansion of clay when injecting to make clay particle generation surface hydration and percolating water occur after water enters the stratum, when the two salinity difference is very big, osmotic pressure strengthens, clay swell phenomenon in stratum is also encouraged evil more, suppress this chemosmotic generation, reduce sticking scholar's hydration swelling and can only take following chemical method, be artificial to make that to inject water identical with formation water salinity or chemical potential, glue the activity of water in soil when identical injecting water activity and stratum, allow and inject water activity and mud shale activity balance, chemical potential equates that at this moment osmotic hydration has not just existed yet.But often difference is very big owing to injecting water salinity and formation water salinity in actual water injection technology is produced, if improve the activity balance that the injection water salinity no doubt can keep system with inorganic salts, but must need a large amount of inorganic salts, be difficult to so in actual applications realize, therefore, method of the present invention is to select for use the injection water of close formation water salinity to inject the stratum, reduce the salinity of injecting water later on more gradually, inject all after dates through some months like this, change normal injection again over to, can keep injecting the salinity and the formation water salinity relative equilibrium of water, promptly kept chemical potential to equate, thereby alleviated greatly because of the extent of damage of reservoir medium clay soil infiltration hydration swelling to permeability, the contiguous water salinity injection stratum way of injecting of raising of the present invention can realize by following approach:

1, at first determines to inject well reservoir formation salinity, add inorganic salts: KCL, Nacl, NH toward injecting in the water according to concentration ₄CL, CaCL ₂, MgCL ₂, make it to reach the balance of injection water and formation water salinity chemical potential in case hydration and expansion of clay effect generation.

2, in each water injection cycle, reduce the consumption that injects inorganic salts in the water according to the salinity of underground reservoir thickness and preliminary treatment water filling radius gradually after, continue water filling in the well.

3, after to the stratum cyclic waterflooding, can make the reservoir salinity approach to inject water salinity, just can change normal water filling (referring in well, inject fresh water) subsequently over to.

The present invention is owing to adopt the salinity gradient water-filling technology of low infiltration sandrock reservoir, alleviate with having prevented the permeability decrease that the reservoir medium clay soil brings because of hydration swelling and influence the drawback of injecting effect, for certain oil field, use the present invention can make oil field water filling steady in a long-term and have cost and hang down characteristics such as easy construction, therefore, can promote the use of new the throwing in the converted production well.

The present invention is provided by following examples:

Embodiment 1:

The alleged method of the present invention need be looked different regions and be selected the inorganic salts consumption.

Flourish 14-38 well gradient water-filling in the oil field, Rong Xing village

The former salinity 6000mg/l in this well reservoir, this well formation water salinity is that 6000mg/l injects water adding NaCL6 kilogram every side then during the 1st cyclic waterflooding, day injection water 60-65m ³, 12 meters of water filling radiuses, water injection cycle 15 days, water filling second round salinity is 3/4 former stratum water salinity, water injection cycle is 12 days, day water filling 60-65m ³, giving the water filling radius is 10 meters; Period 3 water filling salinity is 1/2 former stratum water salinity, water injection cycle 10 days, day water filling 65m ³, estimate 9 meters of water filling radiuses, like this, after three cyclic waterfloodings, change the normal water filling that does not add inorganic salts over to, by the end of in March, 95, the balance water filling 16 months of this well, accumulative total water filling 30,000 sides; Only water filling 4000 is in many ways and compare certain well with certain offset well of the equal conditions of areal.

Embodiment 2: 2 gradient water-filling wells are handed in the oil field, Kailu.

This piece formation water total salinity 3290.57mg/l adopts every 1m during the first gradient cyclic waterflooding ³Injecting water, to add inorganic salts be respectively 2.6kg (NaCL:2.225KG wherein, CaCL ₂0.195kg, (H ₂O) ₈MgCL ₂: 0.130kg) water filling salinity is that 2600mg/l annotated 400 sides in average month and is total to side surplus the water filling 25 days 10000, adopts every 1m during the second gradient cyclic waterflooding ³Injecting water, to add inorganic salts be respectively 16kg (NaCL:1.4Kg wherein, CaCL ₂: 0.12kg (H ₂O) mgcl ₂, 0.80kg), the injection water salinity is 1600mg/L, day annotates 670 side's water, annotates 25 days 16750,16750 side's water altogether, period 3 each rice during gradient water-filling ³Add inorganic salts 1.1kg, be respectively: Nacl:0.961kg, Cacl:0.083kg (H2O) ₈It is 1100mg/l that MgC/l:0.055kg injects water salinity, and day notes 920 side's water were annotated 13800 sides altogether 15 days.Period 4, each rice 3 added inorganic salts 0.6kg during gradient water-filling.Be respectively NaCL:0.525kg, CaCL ₂: 083kg (H2O) ₈It is 1100mg/l that MgC/l:0.055kg injects water salinity, and day notes 920 side's water were annotated 13800 sides altogether 15 days.Period 4 is each rice during gradient water-filling ³Adding inorganic salts 0.6kg, is respectively NaCL:0.525kg, CaCL ₂: 0.046kg, (H ₂O) ₈Mgcl ₂0.029kg inject water salinity 600mg/l, day notes 920 sides annotate 5 days 13800 side's water altogether; Tired degree injects 70 days 55270 side's water, changes the water filling of conventional water source then over to, shared NaCL:66.71 ton, CaCL ₂5.76 ton (H ₂O) mgcl ₂: the 3.83kg ton, inject water salinity respectively by 2600mg/l, 600mg/l, fade to 600mg/l because the method for implanting that has adopted injection water and formation water to move closer to, thereby the reservoir formation water salinity in the just artificial reduction water injection well has significantly reduced low mineralization injects water to formation damage, has prevented that the reservoir medium clay soil from serious the expansion being taken place, and causes the reservoir permeability disadvantage that declines to a great extent, thereby played the water injection rate that has improved oil well, increased the effect of well oil output.

Claims

1, a kind of mineralizing gradient water-filling method for low-permeable reservoir is characterized in that at first determining to inject well reservoir formation salinity when reservoir water filling in well, adds inorganic salts KCL, NaCL, NH in the water toward injecting again according to the salinity concentration ₄CL, CaCL, MgCL ₂According to known underground reservoir layer thickness and water filling radius, reduce the consumption that injects inorganic salts in the water more gradually, and continue water filling in the past well then, after several cyclic gradient water fillings, press normal procedure at last again and recover water filling fresh water the stratum.

2, salinity gradient water-filling method according to claim 1; It is characterized in that being: during 6000mg/l when salinity in the reservoir, in first water injection cycle, per 1 side injects water and adds the NaCL6 kilogram, 3/4 concentration adding NaCL by former reservoir salinity in second water injection cycle prepares injection water injection stratum, the 3rd water injection cycle adds the Nacl preparation by former reservoir salinity 1/2 concentration and injects water injection stratum, after cyclic gradient water filling in three months, and then in well, inject fresh water.

3, salinity gradient water-filling method according to claim 1; It is characterized in that when salinity in the reservoir is 3290.57mg/l, in first water injection cycle, add inorganic salts: NaCL:2.23kg, CaCL whenever annotating side's water ₂0.195kg (H ₂O) ₈MgCL ₂: 0.130kg, add the back and inject water salinity 2600mg/l, each Fang Shui adds inorganic salts NaCL:1.4kg, CaCL in the second gradient water-filling cycle ₂: 0.12kg (H ₂O) ₈Mgcl ₂: 0.80kg, adding the back, to inject water salinity be 1600mg/l, the period 3 during gradient water-filling each Fang Shui add inorganic salts: NaCL:0.961kg, CCL ₂0.083kg, (H ₂O) mgCL ₂0.055kg adding the back, to inject water salinity be 1100mg/l, the period 4 during gradient water-filling per 1 side's water add inorganic salts NaCL 0.525kg, CaCL ₂: 0.046kg, (H ₂O) ₈MgCL ₂0.029kg, add back water filling salinity 600mg/l, annotate 70 days 55,270 side's water altogether.