Application of deep profile adjustment technology in low permeability reservoirs

Deep profile adjustment is to inject a weak gel conditioner into the oil layer that can not only play a certain blocking role, but also have a certain migration ability
.
This weak gel conditioner enters the large pores in the oil layer, which plays a certain plugging role, reduces the ability of the injected water to enter the large pores and flows along the large pores, and makes the injection water turn to the layer or area with more oil content in medium and low permeability, thereby displacing the remaining oil in it; At the same time, due to the low crosslinking strength, this weak gel repellent can continuously move along the large pores to the deep part of the oil layer under the impetus of the subsequent injection water, so that the steering of the injection water continues to extend to the depths of the oil layer, and constantly drive the remaining oil in the oil
layer far from the injection well.
This is a dynamic process
that deepens with subsequent water injections.
Therefore, the ripple volume can be maximized, and the utilization rate of the injection water can be improved, thereby enhancing the recovery rate
.

Well selection for sectional wells

There are currently two main contradictions
in the sectioning block.
First, the contradiction of block injection and production is prominent, the situation that water wells cannot be injected and oil wells cannot be produced is serious, and the formation pressure between each well varies greatly, and it is difficult to effectively control the decline
.
Second, the injection pressure of the partial water injection well in the block is low, and the injection water collects around the wellbore through the high seepage layer, which is easy to cause casing in the area and water
inrush during drilling.

Well selection basis

There are a total of 21 water injection wells with an average oil pressure of 11.
3Mpa, of which 4 wells with injection pressure lower than 10Mpa for a long time, with an average injection pressure of 8.
6Mpa, and the deep profile control project is carried out
around these four wells.
Statistics show that there are a total of 24 first-line oil wells around the 4 sectional wells, all of which are in the medium and high water cut.

It can be seen that the heterogeneity in the well layer is serious, there are high seepage channels, and the contradiction is prominent, and it is necessary to carry out the profile adjustment experiment
.

Profile modulator preferred

In order to ensure that the non-profile adjustment layer is not harmed, the following principles are followed in the selection of the type of profile adjuster: first, the profile adjustment agent is transportable and can enter the deep part of the oil layer; Second, the selection of the particle size of the profile adjuster injection adopts the principle of small to large according to the rise of injection pressure; Third, the profile control agent has a certain plugging ability, prolongs the validity period of the section control well, and prevents the channeling and fingering of the blocking agent, so as not to affect the normal production
of the produced well.

According to the above principles, the secondary glue expansion system with high blocking strength and asphalt particles and montmorillonite were selected for combined cross-sectioning
.

Under ground conditions, silicate, calcium chloride, alum, hydrochloric acid mixture was mixed with partially hydrolyzed polyacrylamide solution, chromium acetate and monomer to form a secondary gelling expansion system containing inorganic pre-gel particles.
The secondary glue expansion system has high strength, and is mainly used in pre-section plugs and sealing section plugs to prevent the channeling and fingering of the plugging agent, so as not to affect the normal production
of the produced well.

Asphalt particle profile adjustment system is a new type of profile adjustment agent independently developed by construction, which has certain fluidity and relative stability, has a good blocking effect, and has the advantages
of not being affected by the nature of carrying liquid, non-toxic and non-polluting the environment, and no equipment corrosion.

Profile scheme design

In order to ensure that the profile regulator can enter the deep part of the formation, achieve effective plugging, and achieve the purpose of controlling the invalid water circulation, the three-stage plug injection method is designed, and the injection concentration adopts the principle of
low-high-high.

The first section plug is a plugging section plug, blocking the large hole in the formation and near the well
.
The second plug is the main plug, which mainly adjusts the plane and intralayer heterogeneity to improve the area ripple efficiency
.
The third plug is a protective plug, which mainly plays a role in preventing breakthrough and ensuring the effect
of section adjustment.

Construction process is preferred

First of all, in view of the problems existing in the development, in order to reduce the contradiction between layers, the general section adjustment construction process
is preferred.
This process has two outstanding advantages: first, in terms of injection wells, the starting pressure difference between each layer can be reduced by general profile adjustment, which can not only reduce the interference between layers, but also reduce the workload of water distribution adjustment in the layer section, which is conducive to expanding the ripple volume and extending the validity period of profile adjustment; Second, in terms of produced wells, the injection and production pressure difference between the small layers is balanced by connecting the injection wells to equalize the injection and production pressure difference, which is conducive to starting the medium and low permeability layers in the perforated well section, and avoiding the sudden advance of the injection water in a single layer, resulting in excessive water rise
.

Secondly, the online injection process of one pump and multiple wells is preferred, firstly, the constant pressure injection method is adopted in the early stage of construction, that is, the maximum injection pressure of the injection well is limited, the injection amount of profile adjustment is not limited, the high permeability layer is injected more, and the low permeability layer is less injected, which is conducive to adjusting the plane contradiction and avoiding the unilateral thrust of the injection water; Second, in the middle and later stages of construction, according to the injection pressure rise rate of each well, the gate control of the injection amount of profile adjustment is adopted, that is, it is conducive to the transport of profile adjustment agent to the deep part of the formation, further expanding the volume of the impact and extending the validity period
of the profile adjustment measure.

Analysis of profiling effects

The deep section adjustment of the section adjustment block is carried out, the depth of the section adjustment is 60 meters, and the injection output profile is adjusted after the section adjustment, which reduces the plane contradiction and achieves good development results, which is specifically reflected in the following aspects:

After the profile, the seepage capacity of the highly permeable layer of the oil layer decreased, and the injection pressure increased significantly, and the average injection pressure increased by 1.
7Mpa
.
In the half year after the adjustment, the average daily oil increase was 1.
8 tons, and the cumulative verified oil increase was 92 tons, and the comprehensive water content was basically stable
.

The oil wells in the profile adjustment block reacted positively after the profile adjustment measures, indicating that the profile adjustment agent blocked the seepage large pores, so that the injected water drove oil in other directions to achieve the profile adjustment effect
.
In the other well, the liquid volume continued to decrease after the profiling measures, and the analysis showed that the high permeability layer of the well was effectively plugged and the water blocking effect was obvious
.

The oil enhancement period of the section control well is calculated according to 18 months, and the cumulative oil increase of the section control well group is expected to reach 300 tons
.
The input-output ratio is 1:2.
3, and the economic benefits are considerable
.

conclusion

Through the application of deep profiling techniques, we have gained the following understandings:

(1) The deep profile adjustment technology in this block is feasible, which can play a role in blocking high-permeability strips and alleviating the contradictions between layers and planes;

(2) Carrying out deep profile adjustment of the oil layer can effectively reduce the trend of production well casing in the region and prevent the occurrence of water channeling in the drilling area, which has certain strategic significance from the economic benefits;

(3) Under the condition that the injection amount of the water injection well after section adjustment is basically unchanged, the injection pressure increases steadily, and the average injection pressure of a single well has increased by 1.
7MPa, indicating that the asphalt particle profile adjustment agent can meet the needs of fracture development oil layer profile adjustment and plugging, and the plugging validity period is long
.