Foamed Diversion in the Chase Series of Hugoton Field in the Mid-Continent
Authors: Logan E.D. , Bjornen K.H. , Sarver D.R. 
Published: December 2007

Abstract
This paper presents an overview of Foam Diversion stimulation treatments utilized in the Permian Chase in the Hugoton field of Southwest Kansas. Potential well candidates are old wells that have been on line +30 years and may still have projected life in excess of 10 years, even though reservoir pressures may be below 150 psi. These older wells were primarily completed open hole with slotted liners. Casing leaks, corrosion, and scaling during the production life of the well necessitate remedial treatments. To effectively treat the thick sequences of carbonate members, adequate isolation or diversion would enhance the treatment by exposing the entire interval to the treatment fluids. This technique utilizes foam as a diverting agent in the matrix treatments as a more practical option to mechanical isolation and ball sealer practices, and an alternative to solid, water soluble diverters.
This paper documents the design and execution of the Foamed Diversion treatments. Treatment profiles are analyzed and the pressure responses to the diversion stages are interpreted. Additionally, this paper documents the production history before and after the treatment on several Chase wells. The production history is used as a criteria for selecting candidates and the post-treatment production history is used to evaluate the effectiveness of the treatment. The main conclusion of this work is that Foamed Diversion on appropriate candidates has proven to be an effective and economical stimulation tool.

Introduction:
The Hugoton Embayment is the far northwest extension of the Anadarko Basin and extends North-South from western Kansas through the Oklahoma Panhandle and into the Texas Panhandle. This play is dominated by the Hugoton field, which makes up part of the Hugoton-Panhandle gas trend (Fig. 1). The sedimentary sequence in the Hugoton received cyclical carbonate and shale deposition during Permian times and total thickness of the series is roughly 250-400 ft. The cyclical series is referred to most commonly as the Chase. The Chase carbonates were originally deposited as bank limestones and were dolomitized after burial and the dolomitization is responsible for secondary porosity development. There are five productive members of Chase and the common names are in order of increasing depth, the Herington, Krider, Winfield, Towanda and Fort Riley (Fig. 2). Although there is a broad variation in reservoir quality and thickness between members, an average of &gt;80 cored wells yielded an average porosity of 13.3% and a permeability of 9 md (KCC. 1985). There is a gas-water contact in the field. The deeper members, the Fort Riley, Towanda and sometimes the Winfield are wet toward the margins of the field. The Krider is sometimes divided into an upper and lower member. The Herington, has the largest aerial extent of the Chase reservoirs because it is the structurally highest member.
The Hugoton field was discovered in the 1920's but most of the drilling activity came in the 50's and 60's. A typical completion during these times would involve conventional drilling and casing placed across the anhydrite at the top of the Chase series. Then a cable tool rig would chisel down 100–200 ft through the Winfield or deeper depending on the area. Some acid work would be performed as members were penetrated with the cable tool rig and during the completion. Sometimes a slotted liner would be hung in the open hole. Original average reservoir pressure was estimated at 467 psi (Relph, 1985). A Chase well with 36–105 ft thick pay, with reservoir characteristics described above and with 200 psi of reservoir draw down would have the potential for 600–1,800 mscf/day in the absence of significant water production or wellbore skin.
Most of the drilling and completions done in the late 60's, 70's, 80's and early 90's came as a result of additional development, replacement wells and later, in-fill wells.
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