US 12,449,395 B2
System and method for real-time drilling fluids pH measuring utilizing electrolyte insulator semiconductor field-effect sensors
Abeer Ateeq Alarawi, Al Khobar (SA); and Rami Adel Sindi, Dammam (SA)
Assigned to Saudi Arabian Oil Company, Dhahran (SA)
Filed by Saudi Arabian Oil Company, Dhahran (SA)
Filed on Mar. 14, 2022, as Appl. No. 17/654,743.
Prior Publication US 2023/0288371 A1, Sep. 14, 2023
Int. Cl. G01N 27/416 (2006.01); E21B 47/00 (2012.01); G01N 27/28 (2006.01); G01N 27/414 (2006.01); G01N 33/28 (2006.01)
CPC G01N 27/4167 (2013.01) [E21B 47/00 (2013.01); G01N 27/286 (2013.01); G01N 27/414 (2013.01); G01N 33/2823 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A system configured to measure pH of a water-based mud (WBM) drilling fluid in real-time in a downhole drilling environment, the system comprising:
a wireless pH sensing device configured to be deposited in the WBM and measure the pH of the WBM drilling fluid, the wireless pH sensing device including:
a capsule shell, wherein the capsule shell is composed of a functional polymer that is sensitive to pH change and wherein the functional polymer is vinyl-benzyl chloride-co-2,4,5-trichlorophenyl acrylate (VBC-TCPA),
a pH sensor of a type having an electrolyte insulator semiconductor field-effect (EIS) structure,
a controller operatively connected to the pH sensor and configured to measure the pH of the WBM drilling fluid using the EIS pH sensor,
a radio-frequency (RF) communications unit operatively connected to the controller and configured to wirelessly transmit the measured pH to a remote monitoring computer, and
an energy unit for powering the controller, the RF communications unit and the pH sensor, and
wherein the controller, the RF communications unit, the pH sensor and the energy unit are encapsulated within the capsule shell, and wherein the capsule shell is made of a material that resists degradation from chemicals, temperatures and pressures of the downhole drilling environment,
wherein the EIS pH sensor comprises:
a semiconductor substrate, wherein the semiconductor substrate comprises Iridium oxide (IrOx),
a metal oxide insulator layer disposed over a first surface of the semiconductor substrate, wherein an outer surface of the insulator layer is exposed through the capsule shell and thereby is in contact with the WBM drilling fluid during use, and separates the WBM drilling fluid from the semiconductor substrate,
a rear-side electrical contact provided at a second surface of the semiconductor substrate that is opposite to the first surface of the semiconductor substrate, and
a reference electrode exposed to the WBM drilling fluid through the capsule shell, wherein the controller is configured to apply a gate voltage between the reference electrode and the rear-side electrical contact and an alternating voltage, and measure one or more electrical parameters representing the pH of the WBM drilling fluid, wherein the reference electrode is an ionic conducting ceramic.