Marker monitoring of oil and gas wells after acid treatments

Abstract

The present disclosure relates to a technique for monitoring the status of an acid-treated oil well by using quantum dot (QD)-based markers. Each of the QD-based markers is a microsphere that is made of hydrophilic or oleophilic materials depending on whether it is intended for water or oil inflow analysis. The hydrophilic microspheres are flushed out with water, while the oleophilic microspheres are flushed out with oil. Each of the microspheres may be filled with the same or different set of QDs. The microspheres are embedded into a porous material which is then placed inside a rigid housing. The housing is provided with a plurality of holes each having a size that is bigger than that of the microspheres. Moreover, the materials of the housing and the microspheres and the porous material are selected such that they are resistant to an acid to be pumped into the oil well.

1 . A production logging apparatus attachable to a downhole pipeline, comprising:
 a housing made of a housing material, the housing comprising a plurality of holes each having a hole size;   a porous material provided in the housing;   a first set of microspheres embedded into the porous material, each microsphere of the first set of microspheres being made of a hydrophilic material and filed with a first type of quantum dots (QDs); and   a second set of microspheres embedded into the porous material, each microsphere of the second set of microspheres being made of an oleophilic material and filled with a second type of QDs,   wherein each microsphere in each of the first set of microspheres and the second set of microspheres has a microsphere size that is less than the hole size, and   wherein each of the housing material, the porous material, the hydrophilic material, and the oleophilic material is resistant to an acid to be pumped into the oil well.   
     
     
         2 . The apparatus of  claim 1 , wherein the first type of QDs is identical to the second type of QDs. 
     
     
         3 . The apparatus of  claim 1 , wherein the first type of QDs has a first illumination spectrum and the second type of QDs has a second illumination spectrum, the second illumination spectrum being different from the first illumination spectrum. 
     
     
         4 . The apparatus of  claim 1 , wherein the microsphere size is selected based on an attachment point of the apparatus to the downhole pipeline. 
     
     
         5 . The apparatus of  claim 4 , wherein the microsphere size ranges from about 0.2 to 10 microns. 
     
     
         6 . The apparatus of  claim 1 , wherein the porous material comprises a polymer or a sponge-like material. 
     
     
         7 . The apparatus of  claim 1 , wherein the housing is made of a housing material selected based on at least one of a type of the downhole pipeline and a type of an oil well into which the downhole pipeline is to be run. 
     
     
         8 . The apparatus of  claim 1 , wherein the downhole pipeline is divided into at least two intervals, and wherein the first type of QDs and the second type of QDs are selected based on one of the at least two intervals where the apparatus is to be attached. 
     
     
         9 . The apparatus of  claim 1 , wherein each of the housing material, the porous material, the hydrophilic material, and the oleophilic material is resistant to hydrochloric acid having a concentration of up to 24 wt. %. 
     
     
         10 . A production logging method comprising:
 attaching at least one production logging apparatus according to any one of  claims 1  to  9  to a downhole pipeline;   running the downhole pipeline into an oil well;   collecting a fluid from the downhole pipeline for a predefined time, the fluid comprising at least one of oil and water;   based on the collected fluid, identifying an amount of microspheres of each of the first set of microspheres and the second set of microspheres which have been flushed out with the collected fluid from the porous material of the at least one production logging apparatus; and   based on the identified amount of microspheres, determining a quantity of at least one of the oil and the water collected from the downhole pipeline for the predefined time.   
     
     
         11 . The method of  claim 10 , wherein said attaching comprises attaching the at least one production logging apparatus to the downhole pipeline by using a fastening element, the fastening element being made of the same material as the housing of the at least one production logging apparatus. 
     
     
         12 . The method of  claim 10 , wherein the at least one production logging apparatus comprises a first production logging apparatus and a second production logging apparatus, and the downhole pipeline has an external surface and an internal surface, and wherein said attaching comprises attaching the first production logging apparatus to the external surface of the downhole pipeline, and attaching the second production logging apparatus to the internal surface of the downhole pipeline in vicinity of the first production logging apparatus. 
     
     
         13 . The method of  claim 10 , wherein the downhole pipeline comprises at least one lateral opening, and wherein said attaching comprises attaching the at least one production logging apparatus on one side of the at least one lateral opening. 
     
     
         14 . The method of  claim 13 , wherein
 the at least one production logging apparatus comprises a first production logging apparatus and a second production logging apparatus,   the first set of QDs of each of the first production logging apparatus and the second production logging apparatus has an apparatus-specific illumination spectrum, and the second set of QDs of each of the first production logging apparatus and the second production logging apparatus has an apparatus-specific illumination spectrum; and   said attaching comprises attaching the first production logging apparatus on one side of the at least one opening and attaching the second production logging apparatus on another side of the at least one opening.   
     
     
         15 . The method of  claim 10 , wherein said identifying comprises:
 obtaining an illumination spectrum for each of the first type of QDs and second type of QDs by illuminating the collected fluid with at least one of an ultraviolet light and a laser light; and   based on the obtained illumination spectra, identifying the amount of microspheres of each of the first set of microspheres and the second set of microspheres in the collected fluid.   
     
     
         16 . The method of  claim 10 , wherein the oil well is a horizontal oil well. 
     
     
         17 . The method of  claim 10 , wherein the at least one production logging apparatus comprises a plurality of production logging apparatuses, and wherein said attaching comprises:
 dividing the downhole pipeline into a plurality of intervals; and   attaching the plurality of production logging apparatuses to the downhole pipeline such that each of the plurality of intervals is provided with one or more production logging apparatuses of the plurality of production logging apparatuses.   
     
     
         18 . The method of  claim 17 , wherein the plurality of intervals comprises a plurality of regular intervals. 
     
     
         19 . The method of  claim 17 , wherein
 the first set of QDs of each production logging apparatus of the plurality of production logging apparatuses has an apparatus-specific illumination spectrum, and the second set of QDs of each production logging apparatus of the plurality of production logging apparatuses has an apparatus-specific illumination spectrum; and   said identifying comprises identifying, based on the collected fluid, the amount of microspheres of each of the first set of microspheres and the second set of microspheres which have been flushed out with the collected fluid from the porous material of each production logging apparatus of the plurality of production logging apparatuses; and   said determining comprises determining, based on the identified amount of microspheres which have been flushed out with the collected fluid from the porous material of each production logging apparatus of the plurality of production logging apparatuses, the quantity of at least one of the oil and the water collected from each interval of the plurality of intervals of the downhole pipeline for the predefined time.   
     
     
         20 . The method of  claim 19 , wherein said determining is performed by using a machine-learning algorithm.