CN104564049B - Polymer flooding gathers the detection method of altering passage - Google Patents

Abstract

The invention discloses a method for detecting poly-channeling channels in polymer flooding, which utilizes the characteristic curve of production-polymerization and oil-increasing index to detect poly-channeling channels in polymer flooding oilfields, and the steps are as follows: the oil production of oil wells is collected at equal time intervals , liquid production and polymer concentration data in the produced liquid; calculate the polymer output, that is, the polymer production; calculate the accumulated oil increase, cumulative production and oil accumulation, and the oil production increase index; calculate the production accumulation oil increase index Characteristic curve: According to the shape of the characteristic curve of the accumulation and oil increase index, the degree of poly-channeling and the channel of poly-channeling can be detected. The method is simple in operation and strong in practicability, and provides technical support for improving the development effect of polymer flooding and further increasing the recovery rate of polymer flooding oilfields.

Description

Detection method of polychanneling channel in polymer flooding

technical field

The invention relates to a method for detecting polychannels in the development process of polymer flooding oilfields, in particular, it provides a detection method for the degree of polychanneling and polychannels based on the dynamic data of polymer flooding oilfield development, in order to improve the polymerization Provide technical support for improving the development effect of physical flooding and further improving the recovery of polymer flooding oilfields.

Background technique

Polymer flooding is an important method to enhance oil recovery in high water-cut oilfields at home and abroad. After the polymer solution is injected into the formation, it can significantly improve the oil-water mobility ratio, reduce viscous fingering, and achieve the purpose of increasing the swept volume and improving the recovery factor. Formation heterogeneity, natural fractures, and dominant channels such as high-permeability channels and large pores formed during long-term water injection production are the main sources of polymer flooding and channeling channels. The existence of polymer channeling channel makes a large amount of polymer enter the oil well along the dominant channel, which seriously reduces the development effect of polymer flooding. To solve the problem of inefficient displacement of polymers, the key is to detect the degree of polychanneling and the channels of polychanneling.

At present, there are many studies on polymer flooding channels, mainly using static analysis method and tracer method, but the static analysis method mainly focuses on the heterogeneity, water cut and oil production of the oil field. In terms of parameters, it cannot accurately reflect the development and production dynamics of the reservoir, so the judgment accuracy is low, and the actual utilization effect is poor. The tracer method requires special testing, which is expensive and affects production. Detection method.

Contents of the invention

Determining the degree of channeling in the oil layer and the type of channels for channeling is the key to effective plugging and further enhanced oil recovery in polymer flooding oilfields. Based on the production dynamic change characteristics of oil wells in polymer flooding oilfields, the invention establishes a set of polychanneling channel detection technology to provide technical support for improving the development effect of polymer flooding and further improving the recovery rate of polymer flooding oilfields.

Explanation of terms:

1. Effective polymer flooding: It means that after the polymer solution is injected into the formation, the swept volume increases due to the decrease of the oil-water mobility ratio. Compared with before the polymer injection, the oil production after the polymer injection increases. When the oil production in a certain month after polymer injection is greater than the average monthly oil production in the three months before polymer injection, it is considered that polymer flooding takes effect at this moment.

2. The pore volume multiple of the injected fluid: refers to the ratio of the injected fluid volume to the pore volume, and the symbol is represented by PV. For example, the reservoir pore volume V ₀ =10000m ³ , the injected fluid volume V=40000m ³ , expressed in PV is $\frac{V}{V_0}=\frac{40000}{10000}=4\mathrm{PV}.$

The present invention provides a detection method for poly-channeling channel in polymer flooding, which utilizes the characteristic curve of poly-accumulation and oil-increasing index to measure the oil field, and the specific steps are as follows:

(1) From the beginning of polymer flooding in the oil field, the oil production, liquid production and polymer concentration in the produced liquid of the oil wells in the polymer flooding oil field are collected at equal intervals;

(2) Calculate the production polymer quantity of the oil well, i.e. the production quantity;

(3) Calculate the accumulative oil increment and accumulative production accumulation from the time when the polymer flooding becomes effective and the output polymer concentration is greater than 0.015 times of the injected polymer concentration;

(4) Calculate the logarithm of the ratio of cumulative production and accumulation to cumulative oil increase to obtain the production and accumulation oil increase index;

(5) Make the characteristic curve of production-accumulation-increasing-oil-increasing index with production-accumulation-increasing-oil index as ordinate, and taking oil field injection fluid pore volume multiple as abscissa;

According to the characteristic curve shape of production-polymerization-increasing oil index, the degree of poly-channeling and the type of poly-channeling in polymer flooding oil field are determined;

If the shape of the characteristic curve of the poly-accumulation and oil-increasing index is concave, the degree of poly-channeling is weak, and there are high-osmotic poly-channeling channels;

If the shape of the characteristic curve of the poly-accumulation and oil-increasing index is S-shaped, the degree of poly-channeling is moderate, and there is a mixed channel of poly-channeling;

If the shape of the characteristic curve of the poly-accumulation and oil-increasing index is convex, the degree of poly-channeling is strong, and there are large-pore type poly-channeling channels.

Collecting the oil production rate, fluid production rate and polymer concentration in the produced fluid of the oil well is a routine operation in the daily work of the oilfield. The time starts from the polymer flooding in the oilfield, and the above-mentioned "equal time interval" is preferably one month.

The above-mentioned "increased oil production index" is the logarithm of the ratio of cumulative oil production (N _p ) to cumulative oil production (N _o ), and the oil production and oil production index can be obtained according to the formula lg(N _P /N _o ). . The production-accumulation-increasing-increasing index is taken as the ordinate, and the pore volume multiple of the injected fluid in the oil field is taken as the abscissa, and a graph is drawn to obtain the characteristic curve of the producing-accumulating and oil-increasing index.

Due to the influence of various uncertain factors, the curves of accumulative oil increment and accumulative production accumulation over time are inevitably not smooth, so the curves need to be smoothed. The commonly used smoothing method is the least squares regression method. This method is simple to calculate, but due to errors or human reasons, the regression is not robust. In order to make the data smoothing robust, this patent uses the robust smoothing method to smooth the above data. For the method, please refer to the reference (Cui Dong. A robust and smooth data processing method [J]. Computer Applications, 2008, 28(7), 1678-1680).

Due to the existence of accumulation and channeling channels in polymer flooding, the production dynamics of polymer flooding oilfields will change, and this change is mainly reflected in the ratio of accumulative accumulation amount to accumulative oil increment in polymer flooding. Accumulation and channeling channels with different development degrees in the oil layer will make the ratio of accumulative accumulation to accumulative oil increase show different changing rules.

The invention uses the characteristics of the curve of the oil production and oil increase index as a method for detecting the channel of polymer flooding and polychanneling. The method is simple in operation and strong in practicability, and provides technical support for improving the development effect of polymer flooding and further enhancing the recovery rate of polymer flooding oilfields.

Description of drawings

Fig. 1 is the characteristic curve of production-polymerization-increase index of oil well 1.

Fig. 2 is the characteristic curve of production-accumulation-increase-increasing index of oil well 2.

Fig. 3 is the characteristic curve of production-accumulation-increase-increasing index of oil well 3.

detailed description

The present invention will be described in detail below in conjunction with specific examples, but the implementation scope of the present invention is not limited.

Take the detection method of polymer flooding channels in Gudong Oilfield as an example. The polymer flooding pilot area has an oil-bearing area of 1.24km ² , geological reserves of 277×10 ⁴ t, an average effective thickness of 12.3m, an average porosity of 29.4%, and an average air permeability of 1320×10 ^-3 μm ² . At present, there are 10 injection wells and 16 effective oil wells in this block of the pilot area.

Gudong Oilfield is a highly heterogeneous oilfield, and there are natural fractures, high-permeability layers and high-permeability channels in the formation. When polymer flooding is used to increase production, the phenomenon of polychanneling is serious and the effect of increasing oil is poor.

The present invention selects 3 wells in a pilot pilot area of polymer flooding in Gudong Oilfield to illustrate the actual application of the polymer flooding channel detection method.

The following are the steps for making the production-accumulation-increase-increasing index characteristic curve of oil well 1:

Select the liquid production rate, oil production rate and polymer concentration from the monthly production report of oil well 1, and calculate the cumulative production accumulation (N _p ) and cumulative oil increase (N _o ); according to the formula lg(N _P /N _o ), to obtain the oil production and increase index; start to record the pore volume of the injected fluid from the injection of the polymer in the test area, take the production and oil increase index as the ordinate, and take the pore volume multiple of the injected fluid as the abscissa, draw a graph, and obtain the polymer production Oil increase index characteristic curve (see Figure 1).

The production-accumulation-increasing-increasing index characteristic curves of other oil wells are made in the same way as that of oil well 1.

The production-accumulation-increasing-oil-increasing index characteristic curve (see Fig. 1) of oil well 1 is an obvious concave body on the whole, and according to the detection method of the present invention, the poly-channeling degree of this well is weak, and there is high-permeability type poly-channeling channel.

The characteristic curve of production-accumulation and oil-increasing index of oil well 2 (see Fig. 2) is an obvious S-shaped body on the whole. According to the detection method of the present invention, the poly-channeling degree of this well is medium, and there is a mixed type poly-channeling channel.

The characteristic curve of production-accumulation-increasing oil index of oil well 3 (see Fig. 3) is obvious convex body on the whole, according to the detection method of the present invention, the degree of poly-channeling of this well is strong, and there is large channel type poly-channeling channel.

When the wells in this block are injected into the polymer solution for production, an isotope tracer is put in for monitoring, and the monitoring and interpretation results are consistent with the detection results of the present invention.

Claims (2)

1. gather a detection method of altering passage for polymer flooding, it is characterized in that, utilize the oily index characteristic curve of the poly-increasing of product to measure polymer flooding oil field, comprising:

(1) implement polymer flooding from oil field, the polymer concentration in the oil production of constant duration collected polymer displacing oil-field oil well, Liquid output and production fluid;

(2) calculate the polymer output of oil well, namely produce poly-amount;

(3) from polymer flooding take effect and output polymer concentration calculate being greater than 0.015 times of injection of polymer concentration tired oil increment with tired produces to gather measure;

(4) ask the poly-amount of tired product and the logarithm of tired oil increment ratio, obtain producing the oily index of poly-increasing;

(5) to produce the oily index of poly-increasing for ordinate, the pore volume injected that fluid is injected in oil field is abscissa, mapping, obtains producing gathering increasing oily index characteristic curve;

Measure polymer flooding oil field according to the oily index characteristic tracing pattern of the poly-increasing of product and gather the degree of altering and poly-type of altering passage;

If described product is poly-increase oily index characteristic tracing pattern spill, then poly-degree of altering is weak, exists highly to ooze that type is poly-alters passage;

If described product is poly-increase oily index characteristic tracing pattern S shape, then poly-degree of altering is medium, has that mixed type is poly-alters passage;

If described product is poly-increase oily index characteristic tracing pattern convex, then poly-degree of altering is strong, has that macropore channel type is poly-alters passage.

2. a kind ofly as claimed in claim 1 gather the detection method of altering passage for polymer flooding, it is characterized in that, also comprise the tired oil increment obtained in (3) or tiredly produce the step that poly-amount and the relation curve of time carry out sane smooth treatment.