SUMMARY

Currently, there is a growing tendency to involve unconventionals in development, therefore drilling, completion and production stimulation technologies are being intensively developed. Cost-effective development of hard-to-recover reserves (HTR) is possible only with the involvement of horizontal drilling and multi-zone hydraulic fracturing.

Due to the fact that conventional methods of PLT of horizontal wells for traditional reservoirs have a number of difficulties when operating on unconventionals, alternative methods for well surveying using flow indicators are increasingly in demand that allow multiphase monitoring of long-term multiphase inflow along a horizontal hole without involving additional equipment, well kill, etc.

The objective of this article was to obtain confirmation on the profile distribution and inflow composition after the MSHF operation for further well intervention planning in the main unconventional of the Russian Federation – the Bazhenov formation.

In a study, the inflow was monitored for oil and water phases in horizontal wells with multistage hydraulic fracturing (from 9 to 15 stages) and the use of the marked proppant. The technology of marker studies of horizontal wells consists in a single placement of high-precision indicators of fluid inflow in hydraulic fractures. After the completion of the MSHF field operation and putting the well into operation, sampling of the reservoir fluid from the wellhead was carried out and they were analyzed on the quantitative distribution of markers of each code corresponding to the interval distribution of oil and water flow rates.

The monitoring of marked wells was carried out periodically for several months. The flow profiles of horizontal holes were constructed on the basis of analysis of samples and analytical data obtained. The results of the work allowed to analyze efficiency of stimulation of horizontal wells for each of the stages of hydraulic fracturing.

Unlike traditional research methods, the main advantage of the presented technology for monitoring the horizontal inflow profile is the lack of need for using special means of device delivery, the use of the technology is not fraught with risks of seizure of equipment and ambiguity of interpretation. It is also important to note that this technology allows monitoring continuously for several years without additional measures.

Comparison of research and monitoring methods is shown in table No. 1. 

Table No. 1.

Comparison of the characteristics of various types of monitoring of well inflows

Type of monitoringClassical set of PLT using CTDistributed fiber optic sensors for online monitoringMarked proppant
Monitoring period A few hours Up to several years (depending on the quality of the optical material and the number of removal of solid particles from the rock) Hydrophilic, oleophilic, gas – more than 3 years (depending on conditions) 
The need to stop or change the well operation mode Yes No No 
Bench tests Yes No Yes 
Number of studies per year 1-2 Continuous monitoring 6-12 (selectively upon customer request) 
Laboratory Not applicable Not applicable Yes 
Multi-hole, multilateral wells or wells with a large distance of the bottom from the vertical Opportunities are limited Yes Yes 
Use in cemented shanks Yes No Yes 
Use in old/new wells Yes For new wells Yes 
Use in open holes Yes (there are restrictions) No Yes (there are restrictions) 
Assessment of the quality of bottom-hole or hydraulic fracturing treatment No KO – Yes Hydraulic fracturing – limited Yes 
The possibility of increasing the efficiency of field development based on the results Yes Yes Yes 
Limitations of the technology Availability of a horizontal hole; Risks of downhole operations; The complex process of running in hole; Repair and maintenance is required; Not a mass decision Limited use in high-viscosity oil; Depends on the success of the hydraulic fracturing operation 
Type of monitoringClassical set of PLT using CTDistributed fiber optic sensors for online monitoringMarked proppant
Monitoring period A few hours Up to several years (depending on the quality of the optical material and the number of removal of solid particles from the rock) Hydrophilic, oleophilic, gas – more than 3 years (depending on conditions) 
The need to stop or change the well operation mode Yes No No 
Bench tests Yes No Yes 
Number of studies per year 1-2 Continuous monitoring 6-12 (selectively upon customer request) 
Laboratory Not applicable Not applicable Yes 
Multi-hole, multilateral wells or wells with a large distance of the bottom from the vertical Opportunities are limited Yes Yes 
Use in cemented shanks Yes No Yes 
Use in old/new wells Yes For new wells Yes 
Use in open holes Yes (there are restrictions) No Yes (there are restrictions) 
Assessment of the quality of bottom-hole or hydraulic fracturing treatment No KO – Yes Hydraulic fracturing – limited Yes 
The possibility of increasing the efficiency of field development based on the results Yes Yes Yes 
Limitations of the technology Availability of a horizontal hole; Risks of downhole operations; The complex process of running in hole; Repair and maintenance is required; Not a mass decision Limited use in high-viscosity oil; Depends on the success of the hydraulic fracturing operation 

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