Key components in the economic evaluation of either production or development prospects are the capital requirements and operating costs of a brine disposal system. Many times, emphasis and attention are given solely to the potential and resulting cash flow from production. Proper planning requires that consideration be given to producing costs. A key component of producing costs is the cost of operating a brine disposal system and the required capital investment. Several Issues must be addressed in order to gain an understanding of the true cost of brine disposal. Generally, in the oil and gas industry, brine is disposed into SWD wells via underground injection. The cost of disposal is dictated by the depth of the disposal interval, the formation characteristics (i.e., thickness, skin, permeability, pore pressure, frac gradient, porosity, injection area), tubular sizes and the maximum allowable wellhead injection pressure. The anticipated fluid volumes to be injected into each well, well life and the number of required injection wells are critical in assessing the true cost of managing an underground injection project. Unrealistic assessments initially can result in less than desired economic consequences. This paper is a description of an underground injection cost model that will provide the capital and operating costs and optimize those costs based on hydraulic fracture design under specified reservoir conditions. Generally, the process to develop brine disposal operating cost include the use of 3D reservoir, fracture and economic models. Various sensitivities must then be run and the results compiled in order to property estimate capital and operating costs. This model incorporates all key parameters and sensitivity analysis is done very quickly with a minimum of input. The model has correlations for many parameters that need to be estimated or calculated utilizing conventional models. This decreases the amount of design time, data required and familiarity with sophisticated models, and allows for easier parametric analysis. The model also allows for the user to input and modify additional parameters if the data is available.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFour large-scale hydraulic fracturing treatments have been successfully conducted in a tight sand gas reservoir in Sichuan, China ranging from 300,000 to 700,000 lbs of proppant per well. Production of gas has been significantly enhanced. Previous hydraulic fracture operations conducted by both western service companies and Chinese Oil Companies did not meet the expected production rate to develop the field. This paper will focus on how the engineering challenges were identified and the designs implemented.
Massive hydraulic fracturing has been successfully applied in tight gas reservoir development. Economic completion of tight gas sands with large hydraulic fracturing treatments requires cost effective and time saving operations. Traditional large fracturing jobs are usually pumped down 5.5" or 4.5" casing to meet the requirement of high pumping rate (30~55bpm). Post-frac snubbing operations are often needed to run tubing and clean out wellbores. Snubbing operations can be costly in terms of investment and time. Annular fracs have been applied in the industry as an alternative completion strategy. However, previously documented annular jobs have been small size, ranging from 40k to 200k lbs of proppant pumped at relatively low injection rates of 15–25 BPM. This paper describes the practices of massive annular fracturing treatments down the 5–1/2" by 2–3/8" annulus used at the Bajiaochang Gas Field, Sichuan Basin, China, as a substitute to fracturing down casing and subsequent snubbing operations. Three treatments have been performed since October 2005. The first job had to be terminated with 70% of the designed proppant (394k lbs) pumped because of the failure of the blast joint. Lessons learned were outlined and modifications were made to the blast joint and wellhead. Subsequent treatments were performed without mechanical failures with 350k and 282k lbs of proppant pumped at 30 to 35 bpm injection rates. The completion cycle time was reduced about 20% with substantial savings of up to $260k in well completion costs. Improved monitoring of bottom hole pressure from static tubing for 3D fracture modeling and effective treatment evaluation were also a benefit. This data has aided fracture design in highly complex fracture stimulation applications. Additional advantages also include: easily circulating out proppant if screen outs occur and more efficient flow back for lower rate wells. Introduction: A tight gas sand exploration and development program has been on going for several years in Chuanzhong Block, Sichuan Basin, China. The reservoir is a fluvial deposit which is located in a slight thrust-fault environment with a possible small strike-slip component. It is over-pressured with micro-Darcy permeability sand (See Figure 1–2). Fifteen wells have been drilled by the operator. All wells are completed in the gas-bearing XX-4 formation at depths of approximately 3150m MD (about 3000m TVD, "S" shape wells are drilled from multi-well pads) by utilizing massive hydraulic fracturing treatments that are the largest and the most complicated in China. The general completion practice at Bajiaochang had been traditional cross-linked gel fracs pumped down 5–1/2" casing at rates from 40 - 50 BPM. Other frac designs including slick water treatment and hybrid fracs have also been used. Due to the potential for waterblocks, post-frac snubbing operations were performed to run production tubing and wash out sand while maintaining an underbalanced wellbore condition. Generally, the completion cycle time was around 41days before handing well over to production. The majority of the fracturing treatments were designed by using the 3D Mfrac model. Real time data has been monitored by linking-up a laptop to the treatment van computer for fracture evaluation and re-design on-site. Lack of bottom hole pressure measurement makes it very difficult to estimate the complex fracture behavior in this high stress environment. Estimation from surface treating pressure, which includes variable friction, may lead to erroneous interpretations.
Key components in the economic evaluation of either production or development prospects are the capital requirements and operating costs of a brine disposal system. Many times, emphasis and attention are given solely to the potential and resulting cash flow from production. Proper planning requires that consideration be given to producing costs. A key component of producing costs is the cost of operating a brine disposal system and the required capital investment.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFour large-scale hydraulic fracturing treatments have been successfully conducted in a tight sand gas reservoir in Sichuan, China ranging from 300,000 to 700,000 lbs of proppant per well. Production of gas has been significantly enhanced. Previous hydraulic fracture operations conducted by both western service companies and Chinese Oil Companies did not meet the expected production rate to develop the field. This paper will focus on how the engineering challenges were identified and the designs implemented.
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