Controlling Water Production In Naturally Fractured Reservoirs With Inorganic Gel F.E. Fragachan, SPE, Schlumberger Dowell, F. Cazares-Robles, Petroleos Mexicanos, J.J. Gutierrez, Schlumberger Wireline and Testing, and G. Herrera, Petroleos Mexicanos
Abstract This paper presents the results of successful applications of inorganic gels to control water production. In naturally fractured reservoirs a case study with hostile high temperatures (260-310 F) found in the Cretaceous and Jurassic dolomitic limestone's of the south east of Mexico is presented together with a water exclusion case from the tertiary sandstones. Importance of gel penetration and selective placement to considerably delay the water percolation to upper intervals in hydraulically communicated intervals is discussed. Included are alternatives for control of gel invasion from the high conductivity fracture network to the tight matrix. Finally, the paper presents a brief discussion of the future of water control in naturally fractured reservoirs.
Introduction Water production in hydraulically communicated formations represents a major problem to the reservoir engineer. The challenge is to shut-off the fractures that are producing "bad" water and are affecting the efficiency sweep of the aquifer "good" water. In addition, the bad water inhibits the oil production from other fractures creating confusion with respect to the actual depth of the oil water contact.
Up until recently, the main approach in these circumstances in the south east of Mexico was limited to abandoning the interval after a cement squeeze, with the hope that moving away from the water the new interval will produce free of -bad- water. However, this technique not only leaves behind considerable reserves of oil, but does not provide assurance, especially in hydraulically communicated intervals, that the water will not finger into the shallower zone. Therefore the key is to provide a remedial solution that effectively and selectively plugs the bad water only, without affecting the oil production.
Unfortunately, such a system is still not available for the existing hostile high temperatures (260- 310 F) found in the Cretaceous and Jurassic dolomitic limestone's of the south east area. Nevertheless, the use of inorganic gels is an alternative when require to pump a fluid with similar rheological properties of the produced water. This way, the gel will preferentially plug the water over the oil and, with deep penetration into the reservoir, would considerably delay the water percolation to the upper intervals.
This paper, following a discussion of water production and control in naturally fractured reservoirs, describes inorganic gels and their applications. Case studies are presented of successful applications of this system in the south east of Mexico including applications for water exclusion in the tertiary sandstones. Finally, alternative applications of this system in workover operations is considered including a brief discussion of the future of water control in naturally fractured reservoirs.
Naturally Fractured Reservoirs: Water Production The production of oil reservoirs today is almost inevitably affected by water production. In fact, this is a direct consequence of the stage of depletion of many of the reservoirs around the world.
In naturally fractured reservoirs water production can cause confusion with respect to the actual level of the oil water contact. Frequently, the irruption of water channeling from the aquifer through a high conductivity fracture is mistaken as invasion of water to the interval. As a result, the interval is prematurely abandoned leaving behind considerable reserves of oil. Thus the importance of understanding the differences between "bad" and "good" water.
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