This process is known as draining effect of caprock. What is additional, the lower of pore stress causes the escalating of matrix tension as well as caprock will deform accordingly. This phenomenon is named prime plate effect. The influence of pore stress depletion while in the caprock is usually calculated through the following equations :First Ailments. Streptozotocin (STZ) ConsiderP=Po?For??0
(five)Based about the above equations, at time tc, the pore stress with respect to z is often offered through the following equations :Pp=Po?(Po?Pr)����,(six)��=(1+z22��tc)erf??cz2��tc?z�Ц�tcexp??(?z24��tc),(7)the place �� = c1k/?��c, Pp is definitely the present pore pressure within the caprock formations; Po would be the unique pore pressure of the caprock; Pr will be the current stress of the depleted reservoir; z will be the vertical distance through the major from the reservoir for the interest level from the caprock; k, , �� will be the permeability, porosity, and fluid viscosity with the caprock, respectively. C1 could be the compressibility on the fluid; c1 could be the unit transformation ratio two.64 �� 10?four; tC would be the growth time, many years.In accordance to (three)�C(7), we will calculate the pore pressure of caprock at distinctive depth, by substituting the outcomes into (1a), (1b), and (1c), the in-situ stress of your caprock immediately after the depletion of your reservoir is gained.
The transform of caprock formation of the specified area in BoHai Gulf Basin is present in Figure 3 primarily based on the geophysics logging data. The involved parameters have the similar value in Part three.Figureselleck chemical 3Influence of advancement on the in-situ stresses of caprock and reservoir with distinctive improvement times.In Figure 3, the filled triangular, square, and circle symbols represent pore stress once the growth time of reservoir is three years, 7 many years, and ten many years, respectively. The open green triangular, square, and circle symbols represent minimum horizontal stresses when the development time of reservoir is three many years, seven years, and 10, years respectively. The open red triangular, square, and circle symbols represent maximum horizontal stresses once the advancement time of reservoir is three years, seven many years, and ten years, respectively.
5. Borehole Stability AnalysisThe in-situ stress calculated by former chapter need to be transformed type the geodetic coordinate programs (one, 2, 3) to borehole coordinate procedure (x, y, z). The coordinate conversion is presented in Figure 4. The conversion relation is as follows:[��xx��xy��xz��yx��yy��yz��zx��zy��zz]=[L][��H000��h000��V][L]T,(8)where L will be the coordinate program transformation matrix. Consider[L]=[cos??��cos??��cos??��sin?��?sin?��?sin?��cos??��0sin?��cos??��sin?��sin?��cos??��].