Physical Model Steamflood Studies Using Horizontal Wells
- P.F. Ahner (Amoco Production Co.) | A.H. Sufi (Amoco Production Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- February 1994
- Document Type
- Journal Paper
- 59 - 66
- 1994. Society of Petroleum Engineers
- 5.4.6 Thermal Methods, 4.1.2 Separation and Treating, 2.4.3 Sand/Solids Control, 1.6 Drilling Operations, 5.8.5 Oil Sand, Oil Shale, Bitumen, 6.5.2 Water use, produced water discharge and disposal, 4.1.5 Processing Equipment, 2.2.2 Perforating
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A series of scaled physical model steamflood tests were made for severalinjection rates and flow configurations on heavy oil systems. A rectangularmodel was built to study drainage areas created by parallel horizontal wells.The model, which was parallel horizontal wells. The model, which was scaled forviscous and gravitational forces, had vertical wells at each corner (twoinjection and two production wells). These wells corresponded to productionwells). These wells corresponded to injectors and producers drilled on a linedrive pattern. Two horizontal wells, each placed between pattern. Twohorizontal wells, each placed between injector/producer pairs, were used toheat the surrounding formation by conduction, thereby providing initialmobility for the fluids. Alternating hot water and steam injection, as well asvarious horizontal well flow schemes, were also studied. These includedinjecting steam from a common source to both the injector/producer pairs, acase which resulted in uneven steam distribution into the model. Line drivesteamflood operation was simulated over both 1.37 and 2.75 acre patterns atsteam injection rates of 427 bbi/day and 650 bbl/day. These tests, whichyielded recoveries of 60-80% of the OOIP, revealed that the process ofinitiating injection using horizontal well heating can be used successfully indraining heavy oil reservoirs.
Thermal recovery methods are the most successful EOR methods in use today.Approximately 80% of all tertiary oil that is produced worldwide is by thermalmethods, primarily steam injection. The main target of these thermal methods isheavy oil and tar sands, although combustion is finding increased considerationin conventional lighter oil reservoirs. In the United States, the majordeposits of heavy oil are in California. Many of these reservoirs had been onprimary production for a number of years prior to being steamed. This allowedgas saturations to develop in the reset voirs, which in-turn, allowed injectionof steam below formation parting pressure. By comparison, the Canadian heavyoil reservoirs have had less primary production. As a result, many of themrequire primary production. As a result, many of them require fracturing toaccomplish steam injection.
In many of the Canadian deposits, fracturing to inject steam is not possibledue to the presence of neighboring wet and/or depleted zones. If such zones arelocated low in the pay, they can be used to inject steam and thereby drain theoverlying oil. However, if these zones are physically isolated from the pay oroccur at the top of the reservoir, they result in inefficient heating of thetarget zone. For such reservoirs, the use of horizontal wells to preferentiallyplace the steam at the base of the preferentially place the steam at the baseof the pay is increasingly being considered. pay is increasingly beingconsidered. The concept of circulating steam in a horizontal well placed nearthe bottom of a vertical injector/producer pair has been proposed in theChevron HASDrive (heated annulus steam drive) process. The horizontal well isnot perforated. process. The horizontal well is not perforated. Instead, it isused to circulate steam by injecting it down a tubing string and flowing backup the casing. The well heats up by the circulating steam and conducts heatinto the formation. This heated zone then forms a one-dimensional conduit forsteam injected into the formation from the injector to the producer (see Fig.1). producer (see Fig. 1). This system was studied experimentally by Sufi usingan element of symmetry of a 7-spot pattern. However, due to the configurationof the element, placing a horizontal well in the system was placing ahorizontal well in the system was equivalent to six horizontal wells radiatingfrom a single vertical injection well. This study revealed an alternatingsteam-water injection technique to increase the injectivity of the heated zoneand allow processing of the overlying oil.
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