US 11,702,933 B2
Method for determining vertical well stratified fracturing crack lengths based on interlayer equilibrium displacement
Chuanzhi Cui, Qingdao (CN); Zhongwei Wu, Qingdao (CN); Zhen Wang, Qingdao (CN); Tongyu Yao, Qingdao (CN); Chuanbao Zhang, Dongying (CN); Guangzhong Lv, Dongying (CN); Yongpeng Ren, Dongying (CN); Gang Cao, Dongying (CN); Xiaoduo Cui, Dongying (CN); and Bo Chen, Qingdao (CN)
Assigned to China University of Petroleum (East China), Qingdao (CN); and Research Institute of Exploration and Development, Shengli Oilfield Branch, Sinopec, Dongying (CN)
Filed by China University of Petroleum (East China), Qingdao (CN); and Research Institute of Exploration and Development, Shengli Oilfield Branch, Sinopec, Dongying (CN)
Filed on Mar. 17, 2020, as Appl. No. 16/821,148.
Claims priority of application No. 201910515902.1 (CN), filed on Jun. 14, 2019.
Prior Publication US 2020/0392842 A1, Dec. 17, 2020
Int. Cl. E21B 43/26 (2006.01); E21B 47/06 (2012.01); E21B 47/08 (2012.01); E21B 49/00 (2006.01)
CPC E21B 49/008 (2013.01) [E21B 43/26 (2013.01); E21B 47/06 (2013.01); E21B 47/08 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A method for determining vertical well stratified fracturing crack lengths based on interlayer equilibrium development, characterized in that, comprising the following steps:
step 1: determining a threshold pressure gradient of each layer,
step 2: establishing a relationship chart between crack half-lengths xf and equivalent well diameters rwe,
step 3: calculating daily oil production rate per unit thickness Qc that meets production requirements,
step 4: calculating the equivalent well diameter rwe of each layer according to the daily oil production rate per unit thickness Qc,
step 5: calculating the crack half-length xf of each fracturing layer according to the equivalent well diameter rwe of each layer;
step 6: performing stratified fracturing according to the crack half-length xf of each fracturing layer;
wherein a calculation formula for determining the threshold pressure gradient of each layer in the step 1 is as follows:

OG Complex Work Unit Math
where, λ is the threshold pressure gradient in MPa/m; μ is oil viscosity in mPa·s; k is formation permeability in μm 2;
wherein steps for calculating the daily oil production rate per unit thickness Qc that meets the production requirements in the step 3 are as follows:
in order to obtain a high fracturing well daily oil production rate Qo and realize the interlayer equilibrium development, which is corresponding to that the daily production rate per unit thickness Qc of each layer is the same, a relationship between Qc, the daily oil production rate Qo after a fractured oil well products and daily oil production rate Qi of each layer is as follows:

OG Complex Work Unit Math
where, Qc, is the daily oil production rate per unit thickness in m3/(d·m); Qo is the daily oil production rate after the fractured oil well products in m3/d; Qi is the daily oil production rate of each layer in m3/d; H is a total thickness of oil reservoirs in meters; and hi is a thickness of each layer in meters.