Downhole Upgrading Athabasca Tar Sand Bitumen Using THAI ? SARA Analysis

摘要

Downhole upgrading of virgin Athabasca TarSand bitumen has been investigatede in a series of 3-Dexperiments using THAI ? ?Toe-to-Heel Air Injection?.The process uses direct line drive, or a staggeredarrangement of horizontal producer wells; in combinationwith either horizontal or vertical wells for gas injection(HIHP or VI2HP). The 3-D tests involved THAI as aprimary process, steam injection aslo as a primarymethod using a new steam flood process, THSF (Toe-to-Heel steamflood), and THAI on a secondary recoverymode, post-THSF. Except for THSF, very high oilrecoveries were achieved: THAI primary: 80% OOIP,THSF: 23% OOIP and THAI secondary: 66.7% OOIP.The low THSF recovery is attributed to the low steamtemperature, because of the low cell opersting pressure.Very significant upgrading of the Athabasca bitumenoccurred during the air injection tests for the majority ofthe experimental period. The API gravity of the producedoil increased by 8 API points and the viscositydecreased to 50 to 1000 mPa.s, compared with theoriginal bitumen viscosity of 1,000,000 mPa.s. Therewas also a substantial decrease in sulphur, nitrogen andheavy metals content of the produced oil. The quality ofthe in-situ upgraded oil was investigated using SARAanalysis (Saturates, Aromatics, Resins, Asphaltenes).This revealed that there was a dramatic increase in thesaturates content of the produced oil, up to 62% to 72%,compared with 15.5% for the original bitumen.