Stimulation of Bypassed Pay Zones in Existing Wellbores (2007)

Stimulation of Bypassed Pay Zones in Existing Wellbores John Walter Moreno; John Walter Moreno New Mexico Tech Search for other works by this author on: This Site Google Scholar Thomas W. Engler Thomas W. Engler New Mexico Tech Search for other works by this author on: This Site Google Scholar Paper presented at the Rocky Mountain Oil & Gas Technology Symposium, Denver, Colorado, U.S.A., April 2007. Paper Number: SPE-107951-MS https://doi.org/10.2118/107951-MS Published: April 16 2007 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Moreno, John Walter, and Thomas W. Engler. "Stimulation of Bypassed Pay Zones in Existing Wellbores." Paper presented at the Rocky Mountain Oil & Gas Technology Symposium, Denver, Colorado, U.S.A., April 2007. doi: https://doi.org/10.2118/107951-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Rocky Mountain Petroleum Technology Conference / Low Permeability Reservoirs Symposium Search Advanced Search AbstractA significant portion of the U.S. gas resources is located in low-permeability, bypassed pay zones, within multilayered sandstone-shale sequences. Acquiring these resources leads to operational and design difficulties in stimulation, particularly if the target zone is bounded above and below by existing producing zones. The objective of this work was to evaluate the impact of adjacent, existing producing zones on the stimulation design and hence production performance of the bypassed payzone.To investigate this problem, a 3D planar, hydraulic fracture propagation model was constructed and superimposed on a 3D flow model. The physical model was comprised of three layers, the top and bottom representing previously stimulated and producing layers, and the middle layer the target or bypassed layer. The impact of lithology, fracture length and total stress variations over time on the fracture conductivity, fracture efficiency and average reservoir pressure were investigated.Evidence of pressure depletion of the target layer was observed due to production of the upper and lower layers. The degree of depletion is dependent on the fracture length and lithology of all of the layers. That is, the ability to propagate a fracture in the target layer was a strong function of the shale content and to a lesser extent, on the hydraulic fracture length of the bounding layers. Increased shale content in the target as well as the bounding layers resulted in a decrease in fracture conductivity of the target layer. However, an increase in fracture length did not necessarily result in a decrease in fracture conductivity of the target layer.The study includes examples of stimulating the Menefee formation in the San Juan basin.IntroductionThe purpose of this paper is to analyze the overall behavior of a multilayer formation, paying special attention to the effect of the current productive zones on the production and stimulation of the bounded, middle layer. In order to evaluate the general lithologic sequences, it is necessary to properly define both the design goals and the design variables that will affect the overall process. Since both production and stimulation will be considered, concepts on hydraulic fracturing (elasticity theory, rheology, continuity and fracture mechanics) and fluid flow (continuity, flow rules, and state equations) must be incorporated for the design goals to be fully coupled. Also, since the common element in both hydraulic fracturing and fluid flow theories is the sensitivity of the medium to stress, the incorporation of non-isotropic permeability tensors and stress maps is necessary to properly describe the system.The model considers a formation consisting of three layers, of which the top and bottom have been stimulated and producing for a period of time. After several years of production, the second (middle) layer will be stimulated, and the entire system (3 layers) producing to the wellbore. The proportion of propped target length among layers has been set to one (i.e., 750 ft) or two (i.e., 1500 ft), and therefore in a X:1–2-2 sequence, the propped length for the first layer will be 750 ft., whereas it will be 1500 ft. for the second and third layers, respectively.The impact of four different types of rocks will be investigated as shown by Figure 1. These, along with the number of layers that compose the system, lead to the selection of only eight possible lithologic sequences, on the basis of the following restrictions:The first and third layer will never be either "sandy shale" or shale; and,Two contiguous layers cannot share the same type of rock.Figure 2 depicts the considered sequences.Out of the above mentioned considerations, a methodology for the development of a fully coupled model is proposed and the corresponding lithologic sequences evaluated and optimized. Keywords: Upstream Oil & Gas, drillstem/well testing, Drillstem Testing, hydraulic fracturing, secondary target, Menefee, sequence, average pressure, Efficiency, shale Subjects: Hydraulic Fracturing, Formation Evaluation & Management, Drillstem/well testing This content is only available via PDF. 2007. Society of Petroleum Engineers You can access this article if you purchase or spend a download.