Two-Wellhead SAGD Scheme Increases Efficiency of Heavy-Oil Development

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 189743, “Case History-Utilizing Dual Wellhead SAGD in Ashalchinskoye Heavy Oilfield in Tatarstan, Russia” by Nukhaev Marat, Baker Hughes, a GE Company, and Siberian Federal University; Rymarenko Konstantin, Baker Hughes, a GE Company; and Latfullin Azat and Amerhanov Marat, Tatneft, prepared for the 2018 SPE Canada Heavy Oil Technical Conference, Calgary, 13–14 March. The paper has not been peer reviewed. Variants of steam-assisted gravity drainage (SAGD) for heavy-oil recovery include crosswell SAGD, single-well SAGD, and horizontal alternating steam drive. The main goal of these modifications is to increase the efficiency of the SAGD process and control steam-chamber development. This paper shares experience gained in the Ashalchinskoye heavy-oil field with a two-wellhead SAGD modification. As a result of a pilot for this technology in Russia, the accumulated production of three pairs of these wells is greater than 200,000 tons. Heavy-Oil Development in Tatarstan, Russia The depletion of the traditional oil reserves of the Republic of Tatarstan makes the development of hard-to-recover hydrocarbon reserves an urgent matter. These reserves include natural bitumen and heavy oil, the reserves of which in Tatarstan’s Permian deposits, according to various estimates, amount to 7 billion tons. These deposits are at a shallow depth. The low mobility of such oil and bitumen is the result of their high viscosity (greater than 10,000 cp). Therefore, thermal methods of heavy-oil recovery are used to ensure an inflow to producing wells. Among such methods are steam injection, huff ’n’ puff, and in- situ combustion. In the operator’s zone of activity, 149 heavy-oil deposits have been identified. The first heavy-oil development projects in Tatarstan began in the 1970s with the implementation of pilots in two deposits using vertical wells. The methods of in-situ combustion, steam injection, and combined steam and gas injection were tested. All pilots in this area were not considered to be successful, because the efficiency of the tested technologies for those particular reservoir conditions was low and the costs of heavy-oil production exceeded the cost of heavy-oil mining. By the end of 2005, approximately 206,000 tons of heavy oil were produced, with an average daily production rate of 0.4 t/D. For the first time in Russia, a pair of horizontal wells for the implementation of SAGD technology was drilled in 1998 at the Mordovo-Karmalskoye field. Because of technological limitations, the length of the horizontal section of the wells could not be increased beyond 150 m. In addition, it was not possible to keep the equal distance between production and injection wells. These problems affected the oil production of the well pair (production did not exceed 4–5 t/D). As a result, achieving profitability was impossible for this first SAGD implementation in Russia. The next trial for SAGD in Tatarstan, with some modifications, was introduced in the Ashalchinskoye heavy-oil field.