Combining Stimulation and Water Control in High-Water-Cut Wells

Abstract

A brownfield in Colombia, produces from the Caballos formation, a highly laminated sandstone formation with permeability of 50 to100 md. The field is under water injection, resulting in calcium carbonate scaling; thus, these wells need to be acidized routinely although the water cut often exceeds 90%. Initially, straddle packers were used to divert the treatments mechanically across the laminated sands, which required a workover rig. To reduce the cost of treating these wells, recent treatments were bullheaded down the tubing casing annulus at the highest possible matrix rates, resulting in mixed results. Water cut increased with no or an insignificant increase in oil production. Hence, a diversion technique/fluid was needed that would provide effective zonal coverage similar to that obtained using straddle packers. The viscous disproportionate permeability modifier (VDPM) fluid was developed for this application. The initial treatments, performed by pumping alternate stages of acid and a VDPM fluid, increased oil production as much as 300% while reducing the water cut by up to 10%. In these cases, the increase in production is equal to or better than wells treated selectively with straddle packers. The use of a VDPM fluid has been shown to be capable of improving zonal coverage, increasing oil production, and decreasing water cut in formations without natural fractures or fissures. During the treatment, the treating pressure increases or remains constant while, in core flow tests, the pressure increases sequentially when injecting acid after each stage of diverter. Despite this, the final effective permeability to oil increases and the effective permeability to water decreases significantly. The VDPM fluid reduces the effective permeability to water up to 80% in a water-saturated core. In the field, the permeability and the length of the interval(s) to be treated determine the number, volume, and viscosity of the VDPM fluid stages based on previous core flow studies. The use of the VDPM fluid has the potential to increase the economic viability of producing this particular field in Colombia and other similar fields. The properties of the VDPM fluid are particularly advantageous when repeatedly treating wells in mature fields on water injection.

Justification of the Need for Pilot Field Tests to Increase Oil Recovery at the Uzen Field

“…Кроме того, большое количество воды добывается вместе с нефтью на зрелых месторождениях, и обводненность может увеличиться до 98% до того, как скважины будут заброшены [8]. Многочисленные нефтяные месторождения по всему миру вступили в стадию обводнения, такие как блок Масила в Йемене [9], нефтяное месторождение Браун в Колумбии [10], а также Шенгли и нефтяные месторождения Дацин в Китае [11].…”

Controlling Losses When Recompleting Low-Pressure Reservoirs

“…3). Meanwhile, viscous DPM (VDPM) fluids have been used successfully to divert matrix stimulation treatments from one interval to another and control unwanted water production after the treatment in wet producers (Jaramillo et al 2010). …”

A Pore-Scale Investigation of Residual Oil Distributions and Enhanced Oil Recovery Methods

“…Additionally, a large amount of water is produced together with oil in mature oilfields and water cut can increase to 98% before wells are abandoned [3]. Numerous oilfields have entered into the high water cut stage all over the world, such as Masila Block in Yemen [4], Brown oilfield in Colombia [5], and Shengli and Daqing oilfields in China [6]. Taking the Shengli oilfield as an example, a survey conducted, in 2015, by the Sinopec shows that the number of wells with water cut in excess of 95% is 6390, which accounts 2 of 16 for nearly 22% of total wells.…”