Hydraulic fracturing and/or matrix acidizing oil and gas wells are often used to stimulate production out of more than one layer in the same wellbore. There are many techniques used to insure that the stimulation treatment is isolated from the other layer(s). These techniques have various levels of cost, complexity, reliability, and time consumption. The limited entry technique is less than optimum as it involves placing entry points in the formation without validation of fluid placement efficiency prior to stimulating.
Embodiments of the invention relate to a method to treat a subterranean formation comprising a wellbore including introducing a tool to a wellbore in a region of low permeability or damage, treating the region of low permeability or damage with a fluid, simultaneously measuring a fluid pressure drop and volume of fluid flow in a particular region, and moving the tool to another region. Embodiments of the invention relate to a method to treat a subterranean formation comprising a wellbore including introducing to a wellbore a tool in a region of low permeability or damage, treating the region of low permeability or damage with a fluid, introducing a diversion agent, and moving the tool to another region wherein the fluid comprises a tracer.
At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation—specific decisions must be made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In addition, the composition used/disclosed herein can also comprise some components other than those cited. In the summary of the invention and this detailed description, each numerical value should be read once as modified by the term “about” (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. Also, in the summary of the invention and this detailed description, it should be understood that a concentration range listed or described as being useful, suitable, or the like, is intended that any and every concentration within the range, including the end points, is to be considered as having been stated. For example, “a range of from 1 to 10” is to be read as indicating each and every possible number along the continuum between about 1 and about 10. Thus, even if specific data points within the range, or even no data points within the range, are explicitly identified or refer to only a few specific, it is to be understood that inventors appreciate and understand that any and all data points within the range are to be considered to have been specified, and that inventors possessed knowledge of the entire range and all points within the range. The statements made herein merely provide information related to the present disclosure and may not constitute prior art, and may describe some embodiments illustrating the invention.
Embodiments of the invention may make a system where multiple zones can be treated with less wellbore operations, more reliable and predictable, and all along at less cost and time using the limited entry technique. Embodiments of the invention are an improvement on the established process of limited entry zone stimulation and resolve the disadvantages of unpredictability, efficiency, and validation of multiple zones being stimulated. This is a method where each entry point can be tested for fluid acceptance quickly, reliably, and inexpensively.
This is a method to simultaneously stimulate and/or acidize multiple zones or multiple fractures in the same zone. The process involves a zone well that will have each zone or several grouped zones to be treated together so that the treatment is isolated and not going to the previously treated/perforated zones. This gives more control over how each zone will deliver its production.
Embodiments of the present invention also allow measurement of a diverter's effectiveness in diverting stimulation and scale treatment fluids from a high permeability layer to a low permeability layer, or from a high pressure zone to a low pressure zone, or from a layer which has a higher fluid mobility to a layer which has a lower fluid mobility. Embodiments of the invention can also be used to evaluate the effectiveness or a diverter to place the injected chemicals more evenly across layers which have different properties and can affect chemical placement. The method allows calculation of volume of fluid injected in the low perm layer vs. the high perm layer, or in the high pressure zone vs. low pressure zone, or in the layer where the fluid has a higher mobility vs. layer where fluid has a lower mobility, and the extent of clean-up, or flow back after the well is put back on production. That is, the different pressure profiles as illustrated by
The method allows calculation of volume of fluid injected in the low permeability layer vs. the high permeability layer and the extent of clean-up after the well is put back on production. Consider a stimulation treatment designed for two reservoir zones intersected by a wellbore. Assume that the top zone is a high perm zone (or a low pressure zone, or a zone where fluid mobility is higher) and the bottom zone is a low perm zone (or a high pressure zone, or a zone where fluid mobility is lower). The objective is to measure the volume of stimulation fluid, or scale inhibition fluid that is injected in the both zones (evaluate diverter efficiency) and to determine the effectiveness of clean-up during flow back. Also, this method allows an alternative to the conventional method using distributed temperature sensors (DTS).
To verify the effectiveness of this system (or the limited entry technique), consider a stimulation treatment designed for two reservoir zones intersected by a wellbore. Assume that the top zone is a high perm zone and the bottom zone is a low perm zone. The objective is to measure the volume of stimulation fluid that is injected in the low perm zone (to evaluate diverter efficiency) and to determine the effectiveness of clean-up during flow back. The evaluation as per embodiments of the present invention would comprise of the following steps:
The tracer concentrations can be measured by monitoring a fluid property related to the concentration, such as, pH, resistivity, density, color etc. The measurements can be made at a single point or at multiple points in the flow path. They can be made in real-time and used in improving the design of the treatment or they can be stored to memory and analyzed later for improving future designs.
The tracer used in monitoring diversion can come from the formation itself. For example, it is possible that in a carbonate reservoir the low permeability zones have more dolomite CaMg(CO3), while the high permeability zones have more limestone (CaCO3). In this case the, Ca and Mg can serve as tracers and their concentrations in the flow back fluid can be used to determine the diverter efficiency.
Once the measurement of the tracer concentration is made, the methods of U.S. Pat. No. 7,658,226 which is incorporated by reference herein in its entirety can be used to calculate the diverter efficiency. Additional embodiments may benefit from the alternatives described in U.S. patent application Ser. No. 12/635,002, filed Dec. 10, 2009, entitled, “Method of Determining End Member Concentrations,” and incorporated by reference herein in its entirety. An alternative method for computing diversion efficiency is by simulating the entire process by assuming a certain diverter efficiency and then comparing the calculated concentrations against the measured values and then iteratively adjusting the diverter efficiency until a good match is obtained between the calculated and measured values.
Variation 1
Can combine the above with a PLT positioned above the lower zone.
Variation 2
Variation 3
Can combine the above (variation 2) with a PLT positioned above the lower zone.
Variation 4
Variation 5
Can combine the above (variation 4) with a PLT positioned above the lower zone.
Variation 6
Variation 7
Can combine the above (variation 4) with a PLT positioned above the lower zone.
Variation 8
Can combine steps 1 to 2 in Variations 2, 4 and 6 above with the following:
Variation 9
Variation 10
Can combine steps 1 to 3 in Variation 9 above with the following:
Variation 11
Can combine the above (Variation 9 and variation 10) with a PLT positioned above the lower zone.
Variation 12
Can combine all the above, with chemical return profile analyses usually sampled at topside to evaluate diverter efficiency and treatment efficiency.
Variation 13
Can combine all the above with flowback properties (rates and concentration) and flow profile of tagged chemicals that may be present in the pre, main and/or post treatment fluid to evaluate diverter efficiency and treatment efficiency over the long term.
Also, when the composition of the downhole fluid sample and the surface fluid sample is analyzed one should analyze the full composition. For example, in addition to looking for T1 and T2, one should look for Ca, Mg ions as well as any component from the diverter stage. Most likely the low perm formation will be different in composition (may contain more dolomite) then analysis of Ca/Mg concentration would allow one to calculate the flow rate from the low perm zone without the need for a PLT. The analysis for the components of the diverter may also lead to a similar result. The concentration of T1 and T2 does not have to be constant. The use of step, or a ramp in T1 and T2 concentration is also possible. The use of mass balance tracer T3 can also be used to confirm the amount of stimulation fluid produced back.
The preceding description has been presented with reference to some illustrative embodiments of the Inventors' concept. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this invention. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.
Furthermore, none of the description in the present application should be read as implying that any particular element, step, or function is an essential element which must be included in the claim scope: the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke paragraph six of 35 USC §112 unless the exact words “means for” are followed by a participle. The claims as filed are intended to be as comprehensive as possible, and no subject matter is intentionally relinquished, dedicated, or abandoned.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB11/52060 | 5/10/2011 | WO | 00 | 2/28/2014 |
Number | Date | Country | |
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61333468 | May 2010 | US |